Patterns of Heredity

______ all traits are simply inherited by dominant and recessive alleles (Mendelian Genetics). In some traits, neither allele is dominant or many alleles control the trait. There are different ways in which traits can be inherited from parents to offspring. Not

5 Different Modes of Inheritance

1. Incomplete Dominance Definition: Neither allele for a gene ____________. Phenotype of the heterozygous offspring will be a ________ of the two homozygous parents. dominates blend

Incomplete Dominance homozygous Ex. A _____________ white flower crossed with a _____________ red flower will produce all _______________ pink flowers. homozygous homozygous heterozygous

Incomplete Dominance NOTATION: Alleles are all capital letters because NEITHER one ____________ the other. So one of the alleles has a ________ (‘) on it to represent an alternate expression of the gene. dominates prime

Always make a _____ to show the genotypes and the resulting phenotypes. Still supports Mendel’s Law of Independent Assortment. KEY

Ex. 1) In a certain species of snapdragons, the combined expression of both alleles for flower color produces a new phenotype – pink. A red snapdragon is homozygous and is crossed with a homozygous white snapdragon. What are the genotypic and phenotypic ratios of this cross?

R R’ P cross = RR x R’R’ G: __________ 100% RR’ P: __________ RR’ RR’ Key: Red = RR White = R’R’ Pink = RR’ P cross = RR x R’R’ G: __________ P: __________ R R’ 100% RR’ RR’ RR’ 100% Pink RR’ RR’

Ex. 2) Then cross the F1 generation and what are the genotypic and phenotypic ratios of this cross?

P cross = RR’ x RR’ G: __________ P: _____________ R R’ RR’ RR’ RR’ Key: Red = RR White = R’R’ Pink = RR’ P cross = RR’ x RR’ G: __________ P: _____________ R R’ 1RR:2RR’:1R’R’ RR’ RR’ 1Red:2Pink:1White RR’ R’R’

2. Codominance Definition: Both __________ are expressed __________ alleles EQUALLY

Codominance Phenotypes of heterozygous offspring are showing both traits! Ex. Red cows crossed with white will generate roan cows. _______ refers to cows that have red coats with white blotches. Roan

Two ____________ alleles (capital letters) are used. Codominance NOTATION: Two ____________ alleles (capital letters) are used. Always make a _____ to show the genotypes and the resulting phenotype. different KEY

In chickens, black-feathered is not wholly dominant over white-feathered, so heterozygous chickens are black and white checkered. Cross two heterozygous chickens. What would the appearance of their offspring be?

P cross = BWxBW Phenotype: B W BB BW BW WW Key: Black = BB White = WW Checkered = BW P cross = BWxBW Phenotype: B W 1 Black 2 Checkered 1 White BB BW BW WW

In shorthorn cattle, the hybrid between red and white is called a roan In shorthorn cattle, the hybrid between red and white is called a roan. What phenotypes would result in the cross of a roan and a white?

P cross = RW x WW Phenotype R W RW WW RW WW Key: Red = RR White = WW Roan = RW P cross = RW x WW Phenotype R W RW WW 2 Roan: 2 White RW WW

3. Multiple Alleles Definition: More than ______________ for a single gene can control a trait. Multiple alleles must be studies by looking at the entire population of species. two alleles

Multiple Alleles Each individual carries only two alleles for any gene (one on each homologous chromosome). In this form of inheritance, a trait can have one gene, but ______________ for that gene. 100 alleles

Multiple Alleles Ex: The human blood group can be any combination of A, B, and O.

Multiple Alleles The alleles are IA, IB and i. Alleles ___ and ___ are ________________. Alleles ___ (“O”) is ____________. A B CODOMINANT i RECESSIVE

NOTATION: GENOTYPES PHENOTYPES Homozygous type A IAIA Type A blood The possible genotypes/phenotypes. GENOTYPES PHENOTYPES Homozygous type A IAIA Type A blood Heterozygous type A IAi Homozygous type B IBIB Type B blood Heterozygous type B IBi Codominant type AB IAIB Type AB blood Recessive type O Ii Type O blood

Multiple Alleles NOTE: the “i” is dropped from the genotype of A and B when the ____________ is written. (Genotype IAI is type A blood) phenotype

Interesting Fact In the US, about 45% of the population is type O, 42% type A, 10% type B and only 3% type AB.

The ABO Blood System

The positive and negative of a blood type is called the ____________, it is totally a separate _______ with RH+ (RR or Rr) and Rh- alleles (rr). If you have the protein = Rh+ If you DO NOT have the protein = Rh- Rh factor gene

Interesting Fact In the US, about 85% of the population is Rh+ and 15% Rh-. Thus the chances of someone being O- (having both ii and rr) would be 45% X 15% = 6.75%.

The most rare blood type would be ______, about 0 The most rare blood type would be ______, about 0.45% if the population. _____ is the universal donor. _____ is the universal recipient. AB- O AB

P cross = IAIB x ii Genotypes: Phenotypes: IA IB i IAi IBi IAi IBi 2 IAi : 2 IAIB IAi IBi 2 Type A: 2 Type B IAi IBi

A father is homozygous blood type A and the mother is heterozygous blood type B, what could be the possible genotypes and phenotypes of their offspring's blood types?

IA P cross = IAIA x IBi Genotypes: IB Phenotypes: i IAIB IAIB IAi IAi 2 IAi : 2 IAIB IAIB IAIB 2 Type A: 2 Type AB IAi IAi

Two Types of Chromosomes Sex chromosomes 1. _____________________: last pair of chromosomes - 23rd pair for humans. XX = _________ XY = _________ female male

Two Types of Chromosomes 2. _________________________ or ___________ All other pairs of chromosomes – 1st – 22nd pairs in humans. Autosomal chromosomes Autosomes

4. Sex-Linked Traits (X-Linked) Other genes besides the alleles for sex are located on the sex chromosomes.

Definition: Those traits will occur _______ frequently in males than females, such as color blindness and hemophilia. MORE

Why? Alleles on a gene may be present on the X chromosome but _________ on the Y. These are called sex-linked traits. absent

This means that ________ may inherit ______ allele for a characteristic and that allele will be expressed, whether it is dominant or recessive, because it is the _______ allele present on their X chromosome. males one only

X-Linked traits most likely will be ____________ to the normal condition and the Y chromosome lacks the gene for a trait, so males have a higher chance of having the disorder. RECESSIVE

These traits generally do NOT show up in __________ since females have genes on both their X chromosomes. females

Notation: The alleles for these traits are written as ______________ on the ___ chromosome ONLY. superscripts X

No ______ alleles are written on the Y chromosome! Ex: Colorblind male = XbY Normal male = XBY _______________ FEMALES are known as __________ XBXb Heterozygous carriers

Ex. 1) Color blindness is a sex-linked trait that is caused by a ______________________. A colorblind man marries a woman that is homozygous for normal vision. recessive allele

P cross = XNXN x XnY XN Xn Normal Y XNXn XNXn Normal XNY XNY What possible types of vision could be found if they had boys? __________ P cross = XNXN x XnY Normal XN Xn Y What possible types of vision could be found if they had girls? __________ XNXn XNXn Normal XNY XNY

Ex. 2) A girl of normal vision, whose father was colorblind, marries a colorblind man. What types of vision could be found in their children?

P cross = XNXn x XnY XN Xn Y XNXn XnXn XNY XnY What types of vision could be found in their children? P cross = XNXn x XnY XN Xn Y 50% Normal vision and 50% colorblindness. XNXn XnXn XNY XnY

5. Polygenic Inheritance Traits are determined by ___________________. They may or may not be found on the same chromosome. Each gene may have more than 2 alleles. MANY genes

The phenotypes may vary depending on the number of dominant and recessive alleles in the genotype.

Traits that show ________________ are a result of polygenic inheritance. Ex. Eye color, skin color, height, facial features. great variability

Environment & Genes environment The ______________ can determine whether or not a gene is fully expressed or expressed at all.

Environment & Genes Internal and external environments can affect phenotypes: Influence of ____________________: ~___________ based on sexes (testosterone, estrogen) Internal environment Hormones

2. Influence of _____________________: External environment ~ temperature ~ light ~infectious agents (viruses, bacteria) ~chemicals ~nutrition

All of these can influence the expression of genes. Environment & Genes All of these can influence the expression of genes.

Karyotypes

What is a Karyotype? ___________ = a test to identify and evaluate the size, shape and number of chromosomes in a sample of body cells. Homologous chromosomes are arranged by ______, __________ patterns and ____________ placement. Karyotype size banding centromere

What is a Karyotype? Extra, missing or abnormal positions of chromosome pieces can cause problems with a person’s growth, development, and body functions.

Examples: Normal Female Normal Male

Why is it done? abnormality defect Determine whether the chromosomes of an adult have an _____________ that can be passed on to a child. Determine whether a chromosome defect is preventing a woman from becoming pregnant or causing miscarriages. Determine whether a chromosome ________ is present in a fetus. abnormality defect

Why is it done? Determine the cause of a baby’s birth defects or disability. Identify the _____ of a person by determining the presence of the Y chromosome. This may be done when a newborn’s sex is not clear. sex

Down syndrome Two copies of an autosomal chromosome fail to separate during meiosis so three copies of that chromosome are made. Trisomy 21

Turner Syndrome Cause: nondisjunction of the sex chromosomes during meiosis so individuals are missing one copy of the X chromosome Affects ONLY females Women are usually short, sexually underdeveloped and sterile. Women with this syndrome function well within society and are not diagnosed until they are assessed for infertility as adults.

Klinefelter syndrome Cause: nondisjunction of sex chromosomes during meiosis so individuals have an extra X chromosome. Affects ONLY males Males are often tall, sexually underdeveloped and may have slight intellectual impairment. Many males with this syndrome function well within society and are not diagnosed until they are assessed for infertility as adults

Jacobs syndrome (XYY) Occurs when a male inherits TWO Y chromosomes from his father instead of one. Cause: unknown. Symptoms: learning difficulties at school and delayed emotional maturity. Males are tall, thin, have acne, speech problems and reading problems.

Pedigrees

Pedigrees ___________ = a valuable tool for anyone working in the field of genetics. Used to show _______________ in families, and resemble a ________ ______. Pedigree relationships family tree

Pedigrees A square represents a male A circle represents a female A vertical line and a bracket connect the parents to their children. A horizontal line connecting a male and a female represents a marriage A circle or square that is not shaded indicates that a person does not express the trait. A shaded circle or square indicates that a person expresses the trait.