Patterns of Heredity

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______ 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

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5 Different

Modes of

Inheritance

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1. Incomplete Dominance Definition:

Neither allele for a gene ____________. Phenotype of the heterozygous

offspring will be a ________ of the two homozygous parents.

dominates

blend

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Incomplete Dominance Ex. A _____________ white flower

crossed with a _____________ red flower will produce all _______________ pink flowers.

homozygous

heterozygoushomozygous

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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

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Always make a _____ to show the genotypes and the resulting phenotypes.

Still supports Mendel’s Law of Independent Assortment.

KEY

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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?

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P cross = RR x R’R’ G: __________

P: __________

Key:Red = RRWhite =

R’R’Pink = RR’

R RR’

R’

RR’

RR’RR’

RR’

100% RR’100% Pink

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Ex. 2) Then cross the F1 generation and

what are the genotypic and phenotypic ratios of this cross?

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P cross = RR’ x RR’ G:

__________P:

_____________

Key:Red = RRWhite =

R’R’Pink = RR’

R R’R

R’

RR’

RR’RR’

R’R’

1RR:2RR’:1R’R’

1Red:2Pink:1White

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2. Codominance Definition:

Both __________ are expressed __________

allelesEQUALLY

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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

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Codominance NOTATION:

Two ____________ alleles (capital letters) are used.

Always make a _____ to show the genotypes and the resulting phenotype.

different

KEY

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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?

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P cross = BWxBW

Phenotype:

Key:Black = BB

White = WWCheckered =

BW

B WB

W

BB

BWBW

WW

1 Black2 Checkered1 White

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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?

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P cross = RW x WWPhenotype

Key:Red = RRWhite =

WWRoan = RW

R WW

W

RW

RWWW

WW

2 Roan: 2 White

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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

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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

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Multiple Alleles Ex: The human blood group

can be any combination of A, B, and O.

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Multiple Alleles The alleles are IA, IB and i.

Alleles ___ and ___ are ________________.

Alleles ___ (“O”) is ____________.

A BCODOMINANT

i RECESSIVE

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NOTATION: The possible genotypes/phenotypes.

GENOTYPES PHENOTYPESHomozygous type A IAIA Type A bloodHeterozygous type A IAi Type A bloodHomozygous type B IBIB Type B bloodHeterozygous type B IBi Type B bloodCodominant type AB IAIB Type AB bloodRecessive type O Ii Type O blood

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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

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Interesting Fact In the US, about 45% of the

population is type O, 42% type A, 10% type B and only 3% type AB.

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The ABO Blood System

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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 factorgene

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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%.

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The most rare blood type would be ______, about 0.45% if the population.

_____ is the universal donor.

_____ is the universal recipient.

O

AB

AB-

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P cross = IAIB x ii

Genotypes:

Phenotypes:

IA IBi

i

IAi

IAiIBi

IBi2 Type A: 2 Type B

2 IAi : 2 IAIB

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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?

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P cross = IAIA x IBi

Genotypes:

Phenotypes:

IA IAIB

i

IAIB

IAiIAIB

IAi2 Type A: 2 Type AB

2 IAi : 2 IAIB

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Two Types of Chromosomes

1. _____________________: last pair of chromosomes - 23rd pair for humans.

XX = _________XY = _________

female

Sex chromosomes

male

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Two Types of Chromosomes

2. _________________________ or ___________

All other pairs of chromosomes – 1st – 22nd pairs in humans.

Autosomes

Autosomal chromosomes

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4. Sex-Linked Traits (X-Linked) Other genes besides the

alleles for sex are located on the sex chromosomes.

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Definition: Those traits will occur _______

frequently in males than females, such as color blindness and hemophilia.

MORE

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Why? Alleles on a gene may be

present on the X chromosome but _________ on the Y. These are called sex-linked traits.

absent

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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.

malesone

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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

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

females

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

superscriptsX

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______ alleles are written on the Y chromosome! Ex: Colorblind male = XbY

Normal male = XBY_______________ FEMALES are

known as __________XBXb

No

Heterozygous carriers

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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

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P cross = XNXN x XnY

XN XN

Xn

Y

XNXn

XNYXNXn

XNY

What possible types of vision could be found if they had boys?

__________

What possible types of vision could be found if they had girls?

__________

Normal

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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?

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P cross = XNXn x XnY

XN Xn

Xn

Y

XNXn

XNYXnXn

XnY

What types of vision could be found in their children?

50% Normal vision and 50% colorblindness.

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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

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

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Traits that show ________________ are a result of polygenic inheritance.

Ex. Eye color, skin color, height, facial features.

great variability

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Environment & Genes The ______________ can

determine whether or not a gene is fully expressed or expressed at all.

environment

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Environment & Genes Internal and external

environments can affect phenotypes:1.Influence of

____________________:~___________ based on sexes(testosterone, estrogen)

Internal environmentHormones

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

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

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Karyotypes

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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 bandingcentromere

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What is a Karyotype? Extra, missing or abnormal

positions of chromosome pieces can cause problems with a person’s growth, development, and body functions.

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Examples:Normal Female Normal Male

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Why is it done?1. Determine whether the

chromosomes of an adult have an _____________ that can be passed on to a child.

2. Determine whether a chromosome defect is preventing a woman from becoming pregnant or causing miscarriages.

3. Determine whether a chromosome ________ is present in a fetus.

abnormality

defect61

Why is it done?4. Determine the cause of a baby’s

birth defects or disability.5. Identify the _____ of a person by

determining the presence of the Y chromosome.

6. This may be done when a newborn’s sex is not clear.

sex

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Down syndrome

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

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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.

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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

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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.

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Pedigrees

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Pedigrees ___________ = a valuable tool for

anyone working in the field of genetics.

Used to show _______________ in families, and resemble a ________ ______.

Pedigree

relationshipsfamily

tree

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Pedigrees

A horizontal line connecting a male and a female represents a marriage

A circle represents a female

A vertical line and a bracket connect the parents to their children.

A circle or square that is not shaded indicates that a person does not express the trait.

A square represents a male

A shaded circle or square indicates that a person expresses the trait.

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