Mendelian Genetics Part 1 AP Biology Mendelian Genetics Part 1

What are genes? DNA segments, inherited from our parents, that code for proteins What is a polypeptide? A protein What processes produce proteins? Transcription and translation

Who was Gregor Mendel? Known as the “Father of Genetics” He was an Austrian monk He was the cook for the monastery, so he had his own garden He observed, grew, and experimented with pea plants

What is a character? An inheritable physical feature Eye color or hair color would be examples What is a trait? The variation of a character Blue eyes or black hair Two alleles are inherited, one from each parent, in order to create the variation

What is an allele? Different versions of a gene A gene is a distinct DNA nucleotide sequence that can make one protein There can be different versions of the same gene, but they all make the same thing (ex. Eye color) Each trait must have two alleles

What are dominant alleles? They are the genes with the genetic information They are represented with capital letters (Tt) What are recessive alleles? They are the genes without genetic information They are represented with lower case letters

What is a true or pure breed? Organisms with only one type of allele for a trait The alleles are homologous (the same) PP or pp

What is hybridization? The creation of an organism that has two different types of alleles for a trait The organism is referred to as a hybrid It has heterozygous alleles

What is a phenotype? The physical traits that can be seen Blue eyes Type A blood Black hair

What is a genotype? The genetic or DNA make-up for the trait

How can you determine a genotype? Perform a test cross Mate a homozygous recessive with the unknown genotype That way no genetic information will be covered up by a dominant allele

What is a Punnett square? A chart that shows all the possible genotypic outcomes that can occur from the mating of two organisms Monohybrid cross 4 squares Dihybrid cross 16 squares Trihybrid cross 64 squares

What is Mendel’s Law of Segregation? During Anaphase I and II, homologous chromosomes of sister chromatids will move independently of each other

What is Mendel’s Law of independent Assortment? Variations are possible on sets of chromosomes, because chromosomes line up during Metaphase I and II independently and randomly

What is probability? Chance The likelyhood of a certain outcome The range is 0 to 1 O is 0% and 1 is 100% .5 would be 50%

What is the best way to assess the probability in a mating cross? Use the Rule of Multiplication Using the parents’ genetics multiplied together to predict the genetics of the offspring

Chance has NO memory.

Gene expression

Gregor Mendel

Character and Trait

Alleles for a gene

One from EACH parent Sperm AND Egg

True breeds & Hybrids

Phenotype vs. Genotype Physical Trait vs. Gene allele type

Test Cross Dominant phenotype, unknown genotype: PP or Pp? Recessive phenotype, known genotype: pp If PP, then all offspring purple: If Pp, then 1 2 offspring purple and 1 2 offspring white: p p p p P P Pp Pp Pp Pp P P Pp Pp pp pp

Monohybrid

Dihybrid

Law of Segregation - Anaphase

Independent Assortment Key Maternal set of chromosomes Possibility 1 Possibility 2 Paternal set of chromosomes Two equally probable arrangements of chromosomes at metaphase I Metaphase II Daughter cells Combination 1 Combination 2 Combination 3 Combination 4

Chance has NO memory.

Mendelian Genetics Part 2 AP Biology Mendelian Genetics Part 2

What produces the phenotype in an organism? The expression of proteins What determines the proteins that will be constructed? Nucleotide sequences that form the codons

What is incomplete dominance? Genetic information is blended The dominant phenotype is not completely covering over the recessive Both phenotypes are seen in a blended version

What is complete dominance? The dominant allele has all the DNA nucleotide information to produce a fully functioning protein This completely suppresses the recessive allele, so that it is not seen at all

What is codominance? Both alleles are seen and are not blended They both are expressed equally

What are multiple alleles? There are several versions of the same basic gene How do multiple alleles work in blood types? Glycoproteins are produced on the surface of the red blood cells One type of glycoprotein is Type A; another type of glycoprotein is Type B If there is no information for making the glycoprotein, then it is Type O

What is Hemophylactic Shock? If two blood types are mixed, the glycoprotein “hands” will not recognize each other One of the blood types will be perceived as foreign, and the white blood cells will begin killing those blood cells

What is the universal donor? This blood type is acceptable by all blood types Type O is the universal donor It has NO glycoproteins on the surface of the cell, therefore, there is nothing for other cells to view as “unrecognizable”

What is the universal recipient? This is the blood type that will accept ANY other blood type Type AB is the universal recipient It has glycoproteins that will recognize the glycoproteins on any other red blood cell

What is pleiotropy? One gene affects many phenotypes Sickle Cell Anemia is a good example This gene affects the red blood cell shape, oxygen carrying ability, resistance to Malaria, etc.

What is epistasis? (one source [epi] affects another location [stasis] A gene at one location on a chromosome affects a gene at another location on the chromosome The phenotypes of hair would be a good example Several genes interact to affect hair color, shape, thickness, texture, etc.

What is the ratio for most dihybrid crosses? 9:3:3:1 What is the ratio when epistasis occurs? 9:3:4

What is polygenic inheritance? Many different degrees of phenotypic outcomes What determines the outcome? The number of alleles you inherit from your parents for that trait Skin color is a good example (how many copies of the same gene were received by the offspring) The number of alleles received are referred to as Quantitative Characters

What is the norm of reaction? The majority of organisms that fall on the bell curve for the trait

What is referred to by the term “multifactorial”? Many environmental factors affect one phenotype This concept is often referred to as “nature vs nurture, or “genetics vs the environment” Most agree that it is about a 50/50 blend Height Intelligence Weight

Phenotype by gene expression

3’ T A C C A G C C G G T A A T A G G G A C C A T T 5’ DNA TEMPLATE 5’ A U G G U C G G C C A U U A U C C C U G G U A A 3’ mRNA METH VAL GLY __ HIST TYR __ PRO TRP __ __ ___ ___ PROTEIN 3’ U A C C A G C C G G U A A U A G G G A C C A U U 5’ ANTI – CODON Sequence Does the DNA Sequence (Million Dollar Blueprint) look like the Anti-codon Sequence? Remember, this is how the ribosome “knew” the Amino Acid was Correct.

Incomplete Dominance

Complete Dominance

Codominance (AB) & Multiple Alleles

Pleiotropy (Sickle Cell)

Epistasis BbCc BbCc Sperm BC bC Bc bc BC BBCC BbCC BBCc BbCc bC BbCC 1 BC 1 bC 1 Bc 1 4 4 4 4 bc 1 BC 4 BBCC BbCC BBCc BbCc 1 bC BbCC 4 bbCC BbCc bbCc 1 4 Bc BBCc BbCc BBcc Bbcc 1 bc BbCc bbCc Bbcc bbcc 4 9 3 4 16 16 16

Dihybrid – Normal 9:3:3:1 ratio

Polygenic Inheritance & Norm of the Reaction AaBbCc AaBbCc aabbcc Aabbcc AaBbcc AaBbCc AABbCc AABBCc AABBCC 20/64 15/64 Fraction of progeny 6/64 1/64

Multifactorial example (Acid in soil changes the color)

Mendelian Genetics Part 3 AP Biology Mendelian Genetics Part 3

What is a pedigree? A family history of traits Squares are males Circles are females Shaded shapes are individuals that are affected Clear shapes are normal individuals

Dominant trait (widow’s peak) . First generation (grandparents) Ww ww ww Ww Second generation (parents plus aunts and uncles) Ww ww ww Ww Ww ww Third generation (two sisters) WW ww or Ww Widow’s peak No widow’s peak Dominant trait (widow’s peak)

Recessive trait (attached earlobe) . First generation (grandparents) Ff Ff ff Ff Second generation (parents plus aunts and uncles) FF or Ff ff ff Ff Ff ff Third generation (two sisters) ff FF or Ff Attached earlobe Free earlobe Recessive trait (attached earlobe)

What are recessive disorders? These are disorders that result because there is NO information for a gene on either of the chromosomes inherited These disorders tend to be harmful They can only occur in a homozygous recessive genotype

What is a carrier? These organisms are heterozygous for a trait They inherited the recessive allele from one parent and the dominant allele from the other parent They do not have the disorder, because the dominant allele is covering it up, but they still have a 50/50 chance of passing the recessive allele to their offspring

What are the characteristics of the recessive disorder called cystic fibrosis? It is the most common lethal genetic disease It affects 1 in 2500 births In Caucasians 1 in 25 is a carrier It creates a faulty protein carrier for the Cl- on the surface of cells in the lungs This causes water to build up in the lungs

What can be done for people with cystic fibrosis? There is no cure for cystic fibrosis Infections in the lungs can be treated with antibiotics Fluid can be drained from the lungs periodically Medications can help reduce the amount of fluid that collects in the lungs

What are the characteristics of the recessive disorder called Tay-Sachs Disease? The disorder causes the lysosomes in the brain cells to be non-functioning The brain cells fill up with lipids and die, because lipids are what brain cells use for energy, but lysosomes have to break them down to release the energy, and the lysosomes cannot do this

Where is Tay-Sachs found to be more prevalent? In the Jewish culture This is because they tend to marry within the culture, so there are a high number of carriers This means the offspring has a greater chance of receiving the recessive gene from both parents Children usually die a painful death by age 5

What are the characteristics of the recessive disorder called Sickle-cell Disease? This is the most common genetic disorder within the black population It affects about 1 in 400 births It is caused by the 6th amino acid being changed from Glutein to Valine (point mutation) This is the primary sequence of one of the proteins needed to make red blood cells

How does the mutated protein affect the red blood cells? They are misshapen from round, disc-shaped to a crescent or sickle shape They cannot carry an adequate amount of oxygen to the cells The sickle cell hemoglobin produces an enzyme that protects the host against Malaria by giving off carbon monoxide

What can be done for individuals that have sickle cell disease? There is NO cure Some medications help with pain and the low oxygen levels

What is the Heterozygous Advantage? Homozygous dominant have normal blood cells but are not resistant to Malaria Homozygous recessive are resistant to Malaria but have sickle disease Heterozygous dominant have normal blood cells but are resistant to Malaria

What are the characteristics of dominant disorders? Only one dominant allele is needed to express the disorder If the individual is homozygous dominant, the disease will usually be much worse What are some examples of human dominant disorders? Achondroplasia Huntingdon’s Disease

What is achondroplasia? Genetic dwarfism It occurs 1 in 10,000 births Most people are homozygous recessive for this disorder, and therefore do not have a genetic code to express the disorder

Achondroplasia is a form of short-limbed dwarfism Achondroplasia is a form of short-limbed dwarfism. The word achondroplasia literally means "without cartilage formation." Cartilage is a tough but flexible tissue that makes up much of the skeleton during early development. However, in achondroplasia the problem is not in forming cartilage but in converting it to bone (a process called ossification), particularly in the long bones of the arms and legs. The most common health problems occur in the spine.

The average height of an adult male with achondroplasia is 4 feet, 4 inches, and the average height for adult females is 4 feet, 1 inch. Characteristic features of achondroplasia include an average-size trunk, short arms and legs with particularly short upper arms and thighs, limited range of motion at the elbows, and an enlarged head with a prominent forehead. Fingers are typically short and the ring finger and middle finger may diverge, giving the hand a three-pronged appearance. People with achondroplasia are generally of normal intelligence.

What is Huntingdon’s Disease? It is a slow degenerative disorder affecting the brain It affects 1 in 10,000 births It does not usually present until around age 40-50 The dominant gene is located on the very tip of autosome 4

Since people have usually already had children before the disease presents, it is important to study family pedigrees in order to know if this disorder is in your genes. The defect on chromosome 4 causes a part of the DNA, called a CAG repeat, to occur many more times than normal. Usually, this section of DNA is repeated 10 to 28 times. But, in persons with Huntington disease, it is repeated 36 to 120 times.

As the gene is passed down through families, the number of repeats tend to get larger. The larger the number of repeats, the higher your chance of developing symptoms at an earlier age. Therefore, as the disease is passed along in families, symptoms develop at younger and younger ages. If one of your parents has Huntington disease, you have a 50% chance of getting the gene. If you get the gene from both your parents, you will develop the disease at some point in your life. You will also pass it on to your children. If you do not get the gene from your parents, you cannot pass the gene on to your children.

What are multifactorial diseases? These are diseases in which the environment also plays a role, along with genetics What are some examples? Heart disease Diabetes Cancer Alcoholism

What are some factors that contribute to heart disease? Genetics Diet Alcohol Smoking Stress

What are some causes of diabetes? Genetics Diet Race Type 2 diabetes occurs more frequently in African Americans, Alaska Natives, American Indians, Hispanics/Latinos, and some Asian Americans, Native Hawaiians, and Pacific Islander Americans than it does in non-Hispanic whites.

What are the causes of cancer? Genetics Life style habits

What are some causes of alcoholism? Genetics (abnormal levels of serotonin and dopamine may contribute) Lifestyle (frequenting places where drinking occurs and being around other drinkers) Mental state (frustration, anger, depression, anxiety, and stress may contribute)

What is penetrance? The percentage of individuals with a certain genotype that actually present the expected phenotype An example would be Huntington’s Disease 95% of individuals that have the dominant allele actually present the disease 5% do not express the disease Therefore, there is a 95% penetrance for the Huntington’s allele

What is expressivity? This refers to the degree to which the allele is expressed or seen Expressivity is more severe when the genotype is homozygous (because that means the individual received TWO copies of the allele)

Sickle- Cell

Achondroplasia

Mendelian Genetics Part 4 AP Biology Mendelian Genetics Part 4

Where are genes found? On chromosomes What two types of chromosomes are associated with humans? Autosomes Sex chromosomes From where does an individual get its chromosomes? They are inherited from the parents

What are linked genes? These are genes that are usually inherited together as a linked unit on the same chromosome These usually refer to genes on the autosomes (Chromosomes 1-22)

Who is Alfred Sturtevant? He was the pioneer of genetic mapping What is genetic mapping? Locating the position of genes on chromosomes

Chromosome 1

How did Sturtevant determine the location of genes on chromosomes? How used the crossover rates of the chromosomes The smaller the rate of crossover, the closer the genes were to each other on the chromsome The higher the rate of crossover, the farther apart the genes were to each other on the chromosome He measured the loci (locations) of the genes in centimorgans, also called map units Sturtevant named this unit in honor of his genetics teacher, T. H. Morgan

What are sex-linked genes? Genes found on the sex chromosomes 95% of the time they will be on the X-chromosome This is because both sexes have at least one X-chromosome Hemophilia is a recessive disorder H is dominant (normal; no disease) h is recessive (will cause disease) #1-female-will not have disease #2-male-will not have disease #3-female-will not have disease #4-male-will have disease **Females rarely get the disease Would have to be XhXh to have it 1 2 3 4 Females are XX (homologous); Males are XY (heterologous)

How are sex chromosomes different from other chromosomes during crossover? There is very little crossover with sex chromosomes When is the sex of an organism determined? At conception or the moment of fertilization Fertilization occurs when either a sperm X chromosome or a sperm Y chromosomes combines with the X chromosome of the egg

What type of sex characteristics do all organisms have at first? Everyone starts out female This is why everyone has nipples When does the change occur? Around 2 months of development The Y chromosome gene becomes active to make testosterone Testosterone is made from estrogen

What happens to testosterone after development is completed? It is turned off until puberty At puberty it is turned back on to make the secondary sex characteristics (facial hair, muscle mass, Adam’s apple, larger bones, etc.) What are primary sex characteristics? The sex organs and gonads

Like any other genetic disorder, sex-linked genetic disorders have…… No cure What are some examples of sex-linked genetic disorders? Color blindness Hemophilia

What is color blindness? A faulty recessive gene on the X chromosome cannot make the protein that absorbs certain wavelengths of light (which determine color) in the cones on the retina of the eye The most common is red/green color blindness, in which both colors appear gray

What is hemophilia? The name means “love of bleeding” Individuals have a faulty recessive gene and cannot make the protein that produces the Anti-hemolytic Factor This is the clotting factor The individual could bleed to death

Why is hemophilia associated with the “Royal Blue-bloods of Europe”? Because they interbred to keep the crown “in the family”, and by doing so, the offspring had a much greater chance of getting two recessive genes for hemophilia Or just one, if a male

What can be done for hemophiliacs? They must keep AHF (clotting factor) with them at all times, in case of injury They must take a shot of AHF the moment they start bleeding, or even if they get a bruise

Who does hemophilia affect? Mainly males Even if they get the recessive gene on an X chromosome, there is nothing on the Y chromosome to counteract it Can females get hemophilia? Yes, but they would have to receive two recessive genes, one on each X chromosome If a female receives only one recessive gene, she will be a carrier, but will not have the disorder

Why does hemophilia seem to skip a generation? Because the mother is usually only a carrier Therefore, the trait does not present in her Then, if she has a son, he can be affected

What kind of genes do not follow Mendel’s Laws of Inheritance at normal or expected rates? Linked genes Sex-linked genes Mendel’s laws were really referring to one chromosome….not pairs of chromosomes, which is what we inherit What is associated with variation? Crossover frequency Which chromosome is referred to with sex-linked? The X chromosome only

Genes on Chromosomes

Autosomes and linked genes

Linkage Map based on Crossover frequency Recombination frequencies 9% 9.5% 17% b cn vg Chromosome

Locus Gene Maps

Sex –Linked Female – TWO Xs

Sex-Linked Male – ONE X

One from EACH parent Sperm AND Egg

Pedigree of Color Blindness

Pedigree of Hemophila

Mendelian Genetics Part 5 AP Biology Mendelian Genetics Part 5

What are some examples of gene mistakes? Point mutations Reading frame mutations

When can chromosomal errors occur? During mitosis or meiosis During Anaphase when the chromosomes are moving During crossover when DNA segments are moving

What are some types of errors that can occur with the chromosomes? Chromosome number Chromosome structure What is aneuploidy? An abnormal number of chromosomes What causes this abnormal number of chromosomes? Nondisjunction during Anaphase

What is nondisjunction? A failure of chromosomes to separate during Anaphase What are some of the results of nondisjunction? Trisomy Monosomy Polyploidy

What is trisomy? Having three of one kind of chromosome in a cell, instead of two

What is monosomy? Having only one chromosome in a cell instead of two Turner’s Syndrome

What is polyploidy? Having extra sets of chromosomes Usually deadly in animals Plants unaffected Bigger fruits Larger flowers

What usually changes the individual chromosome structure? Faulty crossover What are some examples of faulty crossover? Deletion Duplication Inversion Translocation

What occurs during deletion? A chromosome segment will be missing on one chromosome, because it got stuck on the other homologous chromosome during crossover

What occurs during duplication? Two copies of a segment of the chromosome will be on one chromosome and missing on the other homologous chromosome

What occurs during inversion? A chromosome segment is turned around backwards during crossover

What occurs during translocation? A segment from one chromosome becomes attached to a different autosome

What is a syndrome? Possessing identifying traits of a particular genetic disorder What are some examples of human genetic syndromes? Down’s Syndrome Turner’s Syndrome Edward’s Syndrome Crouzon Syndrome

What is Down’s Syndrome? Trisomy 21 An extra copy of chromosome 21 (three instead of two) Often caused when older women have babies What are some identifying characteristics? Mental retardation Flat face Squinting eyes Smaller stature

What is Crouzon Syndrome? A faulty protein causes abnormal growth of the bones of the jaw

What is Treacher Collins Syndrome? Characteristics are a high arched palate, malformed ears, bird or fishlike face, lower eyelids, and deformities of the jaw bones

What is extranuclear DNA? DNA that is outside the nucleus This DNA would be inside other organelles, such as chloroplasts, mitochondria, and other plastids This DNA can only be inherited through the mother, because the egg cell alone has cytoplasm and organelles (sperm only has DNA) These sources are cloned (exactly alike), so they help in identification

What is Mitochondrial Myopathy? Mitochondria that lack the ability to make adequate amounts of ATP They have faulty DNA segments for making some of the enzymes or proton pump proteins Individuals that have this disorder are usually very tired all the time

Non-Disjunction

Trisomy 21

Chromosome Structure Errors

Extranuclear DNA (This DNA CAN can affect an organism)