Patterns of Heredity Ch. 4 Genetics!!

Do Now!!  True or False?? Color blindness is more common in males than in females. A person may transmit characteristics to offspring which he/she does not show. Certain inherited traits may be altered by the stars, planets or moon early in development There is such a thing as “werewolf syndrome” that could be linked to genes.

Hypertrichosis (“werewolf syndrome”) Stephen Bibrowski as “Lionel the Lion-faced Man”

Objectives To define heredity and inheritance To determine how we inherit traits from our parents To take an inventory of our class’s traits!

Genetics = the study of heredity by which traits are passed from parents to offspring

Heredity The passing of genes/traits from parents to offspring. Many of your traits, including eye color, shape of your eyes, texture of your hair, height, and weight resemble those of your parents!

What is a gene? A unit of heredity that occupies a specific location on a chromosome and codes for a particular product. A specific segment of DNA found on the chromosome

Thanks Mom and Dad! We inherit genes from our parents Those genes code for the traits we express Most traits are coded by more than 1 gene: Ex: Height

Homologous Chromosomes A pair of chromosomes are called homologs (homo meaning same) Homologous chromosomes have the same size, structure, and genetic information.

What are alleles? Versions of a gene that occupy corresponding positions on homologous chromosomes We inherit 2 alleles for each gene: 1 from mom and 1 from dad!!

Sex Chromosomes We have 23 pairs of chromosomes 1 pair are known as the sex chromosomes, which determines the sex of the offspring Males = XY Females = XX

Do Now!!  What is an allele? What are homologous chromosomes? Give an example of a trait that is coded by more than one gene!

Objectives To discuss the importance of Gregor Mendel To identify the parts of Mendel’s pea plant experiments To differentiate between dominant and recessive alleles

The history of Gregor Mendel Father of genetics! Bred different varieties of garden pea. First to develop rules that accurately predict patterns of heredity. Discovered how traits were inherited

Pollination – transfer of pollen from anthers to stigma in flowers 1) self pollination occurs within the same flower or same plant 2) cross pollination occurs between different plants

Pea plants = great subject to study heredity Several traits exist in two clear different forms. Ex: Flower color was either purple OR white

Pea plants = great subject to study heredity (cont.) The male and female reproductive parts are enclosed within the same flower. It is easy to control mating by allowing a flower to fertilize itself (self fertilization), or you can transfer pollen to another flower (cross pollination).

Pea plants = great subject to study heredity (cont.) The garden pea is small, grows easily, matures quickly, and produces many offspring. Results can be obtained quickly.

Steps in Mendel’s research… Allowed each garden pea to self-pollinate for several generations to ensure “true-breeding” for that particular trait. *P Generation = parental generation

Steps in Mendel’s research (cont.) 2. Mendel then cross-pollinated two P generation plants that had different forms of the trait (purple and white flower). The offspring from that were called the F1 generation. *F 1 generation = Filial generation (of son or daughter)

Steps in Mendel’s Research (cont.) 3. Allowed the F1 generation to self-pollinate and those offspring are called the F2 generation. * F2 Generation = Filial generation 2

Ratio of Mendel’s Research P Generation had a true-breeding purple and white flower F1 generation: ALL purple flowers F2 generation: 705 purple flowers and 224 white flowers. That is a ratio of about 3:1

Mendel’s Crosses with Pea Plants X Pure tall plants Pure short plants parental generation P1 Cross Pollination first filial generation All Tall plants F1 Self Pollination second filial generation 787 tall plants, 277 short plants F2 3 to 1 ratio

Mendel’s 3 Laws of Inheritance Law of Dominance- Each trait is controlled by 2 factors: Dominant- what is expressed Recessive- masked in presence of dominant

*Reminder!! T = tall t = short Alleles are alternative forms of a gene. Can be dominant or recessive! Dominant capital letter (shields recessive trait) Recessive Lowercase letter (usually hidden) T = tall t = short

Mendel’s 3 Laws of Inheritance 2. Law of Segregation-Each allele separates into different gametes Ex. Ww – one W goes in one sperm and the other w goes into another sperm Ww w W

Mendel’s 3 Laws of Inheritance (cont.) 3. Law of Independent Assortment- Gene pairs (homologous) will separate randomly into gametes during meiosis (Why? Random orientation of homologous pairs at the metaphase plate)

Do Now!!  1 2 3 4 5 7 6 What are Mendel’s 3 laws of inheritance? What is the difference between dominant and recessive traits? Below is a chart of Mendel’s experiment. Fill it in!: 1 2 3 4 5 7 6

Objectives To differentiate between phenotype and genotype To define homozygous and heterozygous To practice monohybrid punnett squares

Phenotype: the physical appearance of a trait Phenotype vs. Genotype Genotype: The set of alleles that an individual has (not always obvious) Phenotype: the physical appearance of a trait

Homozygous – when both alleles of a pair are the same dominant TT homozygous recessive tt

Heterozygous – when both alleles of a pair are not the same (tall) Tt

Heterozygous Homozygous Different alleles present Ex: Bb Two of the same alleles Ex: BB or bb Can be homozygous recessive or homozygous dominant

Recessive vs. Dominant Recessive: The trait not expressed when the dominant form of the trait is present Dominant: The expressed form of the trait when present (even if it is just 1 allele)

In dogs, black fur is dominant over white fur color. B = black fur b = white fur WOOF WOOF! bb BB or Bb

Think - Pair - Share If Jon Snow is heterozygous for black hair… (H=Black, h=blonde) 1. What is Jon Snow’s genotype? 2. What is Jon Snow’s phenotype? Beyonce is BB. (B= brown eyes, b=blue eyes) 1. What is her genotype? 2. What is her phenotype? 3. Is she heterozygous or homozygous? Explain.

Probability Probability calculations can predict the results of genetic crosses. It is the likelihood that a specific event will occur. = number of one kind of possible outcome Total number of all possible outcomes Example: If you flip a coin, you will have 1 outcome, but two possible outcomes. Your answer would be ½.

How do you write a ratio? When flipping a coin and it lands on tails  ½ or 1:2 Genotypic ratio: What is genetically written Phenotypic ratio: what physical traits you would see Phenotypic Ratio 3:1 3 Black : 1 White

Punnett Square A diagram that predicts the outcome of a genetic cross by considering all possible combinations of gametes in the cross Crossing only 1 trait is called a monohybrid cross. Crossing 2 traits is called a dihybrid cross.

Punnett Square Rules! Assign symbols Determine parents genotype Draw punnett square Place gametes on left + top of square Fill in punnett square Analyze + answer questions

Practice Punnett Squares: Monohybrid Cross Phenotypic Ratio and %: Genotypic Ratio : T: Tall plants t: Short plants

Practice Punnett Squares: Monohybrid Cross R: round seeds r: wrinkly seeds Phenotypic Ratio and %: Genotypic Ratio :

Crosses that involve 2 traits

Practice Punnett Squares: Dihybrid Cross Phenotypic Ratio: Genotypic Ratio :

Gene Linkage and Polyploidy There are several genes on a chromosome Gene Linkage: When two genes are close to each other on the same chromosome

Gene Linkage Linked genes on a chromosome results in an exception to Mendel’s law of independent assortment Linked genes usually do not segregate independently

Drosophila melanogaster (Fruit Flies) First organism with linked genes Linked genes typically travel together during crossing over

Chromosome Map A map of genes on a chromosomes Crossing over occurs more frequently between genes that are far apart

Strawberries are octoploid!! Polyploidy Cells that contain more than 2 homologous sets of chromosomes Ex. A triploid organism (3n) - means that it has three complete sets of chromosomes. Strawberries are octoploid!!

Matching

Pedigree Shows history of a trait in a family Allows researchers to analyze traits within a family

In a pedigree… You can see how a genetic disorder runs in a family. Carriers are individuals who are heterozygous for an inherited disorder but do not show symptoms. Carriers can pass the allele for the disorder to their offspring

Figure out each genotype!

Figure out each genotype!

DO NOW!!  Fill in genotypes! B: Brown eyes b: blue eyes

Multiple alleles – 3 or more alleles that control a trait Example: blood type! Possible alleles: IA, IB, i Which genotypes are heterozygous? Homozygous? GENOTYPES RESULTING PHENOTYPES IAIA IAi Type A IBIB IBi Type B IAIB Type AB ii Type O

Antigens vs. Antibodies Antigen: substance foreign to the body that causes an immune response: Can act as surface markers EX: type A antigens on surface of type A blood cells Antibody: protein that reacts with specific antigen: EX: Type B blood contains anti-A antibodies

Which is the universal donor? Universal acceptor?

Determine Blood Type Determine the possible offspring of the following crosses 1. AB and O 2. Homozygous A and heterozygous B 3. AB and AB

Do Now!!  Determine the possible blood types: Cross homozygous A and heterozygous B AB x AB

Polygenic Traits Polygenic traits arise from the interaction of multiple pairs of genes.

Incomplete dominance Heterozygous phenotype is intermediate between two homozygous phenotypes: In between two extremes Heterozygous phenotype appears blended. Ex: Four O’clock flowers Red + White = Pink

Examples!

Codominance Both traits are expressed (no blending) Ex: Roan Cows white hair (HW) is codominant with red hair (HR) cows with genotype (HRHW) have coats with a mixture of red and white hairs (roan) Red + White = RED AND WHITE

Examples!

Sex Linked Traits Traits located on the sex chromosomes (X or Y) X linked: gene is located on the X chromosomes Y linked: gene is located on the Y chromosome Ex: color-blindness is X-linked!

Sex-Linked Traits A man who is color blind marries a woman that is heterozygous for color blindness. What is the chance of having a color blind boy?