Flashcard Warm-up

Genotype vs.

Phenotype

Genotype is the genetic makeup (AA, Aa, or aa)

Phenotype is the physical trait, a result of the genotype

AlleleFor any trait, such as

hair color, there are different forms of the protein that create the different hair

colors. Each different form is called an allele. We use

capital letters to represent dominant

alleles and lower case letters to represent the

recessive alleles.

Unit 10- GeneticsWhere did my traits come from??

Inheritance of chromosomes

Egg + sperm zygote

egg

sperm

zygote

fertilizationmitosis &development

meiosis

Traits: physical or physiological characteristics; like eye color, or blood type◦Phenotype:

individual’s observable trait; brown hair

Genes: Portion of DNA that make proteins that control our traits and are found on chromosomes. ◦Chromosomes exist in

pairs, one from sperm one from egg.

Alleles: different versions of genes; blue eye gene, brown eye gene; we use letters to represent alleles◦Alleles are inherited

separately from each parent.

How does this work?

eye color(brown?)

hair colo

r

hair colo

r

eye color

(blue?)

Paired chromosomes have same kind of genes◦ but may be different alleles

Genes affect what you look like

X BB

bb

Bb

Bb

Bb

Bb

Where did the blue eyes go??

Genes affect what you look like…

X Bb

bb

Bb

Bb

bb

bb

Why did the blue eyes stay??

What is a genotype and how do we write it?Genotype: the genetic makeup

◦ (the alleles you received from mom and dad)

Examples of genotypes:Homozygous: Identical copies;

AA – homozygous dominant aa - homozygous recessive

◦Dominant genes mask or hide recessiveHeterozygous: one dominant and one

recessive; Aa2 people can have the same

appearance but have different genetics: BB vs Bb

Mendelian Genetics:

Gregor Mendel : Father of Genetics◦Studied pea plants--- 1866◦Why pea plants?

Mendel’s PrinciplesThree Principles: 1. Principle of Dominance: dominant alleles

can mask/ hide recessive alleles◦ Homozygous dominant: AA; Dominant trait is

expressed◦ Heterozygous: Aa; dominant masks/hides recessive

and is expressed◦ Homozygous recessive: aa; recessive trait is

expressed2. Principle of Segregation: to separate, each

parent can only pass on one allele per trait3. Principle of Independent Assortment: genes

on separate chromosomes are passed on independently from one another.

Principle of Segragation

Principle of Independent Assortment

Punnett squaresBb x Bb

male / sperm

fem

ale

/ e

gg

s

X

BB

Bb bb

BbB

b

B b

Flashcard Warm-upMendel’s Principles of

Inheritance:

Use your notes from yesterday to write down and briefly EXPLAIN the three principles

Punnett Squares

Monohybrid cross: a Punnett square involving only one trait; 4 boxes

Dihybrid cross: a punnett square involving two traits; 16 boxes

Flashcard Warm-Up Trait:

◦Free earlobes- dominant = F◦Attached earlobes- recessive = f

1. A woman has free earlobes, what are two possible genotypes she might have?

2. The genotype for a man is Ff, what is his phenotype?

3. What is a gene?

Flashcard Warm-up

CodominantIf two alleles are

codominant, they are equally strong. Both alleles would

be seen in the phenotype. An

example is crossing a black chicken with a white chicken and the offspring having

both black and white feathers.

Incompletely

DominantNeither allele is

dominant, so when both alleles are present they

mix or blend. These alleles are written with ONE letter that has a

prime ‘

Non Mendelian Genetics: Codominance:

Both alleles are equally dominant and will be expressed

Phenotype: 3 possibilities

Genotype: 2 Capital letters; BB, WW, or BW

Red hair is dominantRR

Roan is a mixture of red and white hair-RW

White hair is dominantWW

Codominant Example:Cross a black cow with a white

cow. Both hair colors are dominant.

Incomplete DominancePhenotype: neither allele is

completely dominant to mask the other

Genotype: heterozygous RR’ results in a blended phenotype , capital letters for both traits and use a prime ‘ symbol for one

RR RR’ R’R’

Incomplete Dominance ExampleCross a white flowered plant with

a pink flower. Both white and red are incompletely dominant.

Ticket Out the Door

A) If feather color in a species of birds in codominant, cross a white bird with a black and white spotted bird. List all possible phenotypes.

B) If fur color is incompletely dominant, cross a gray fur dog with a black dog. List all possible phenotypes.

Flashcard Warm-up

Sex chromosomes

For humans, the last set of chromosomes are the sex

chromosomes that determine the gender. Females have two X

chromosomes and males have one X and one Y. Examples of sex-linked traits are colorblindness and hemophilia, these

traits are carried on the X chromosome.

Polygenic trait

trait determined by many genes, results in a wide range of

phenotypesExamples include height, skin color,

hair color

Multiple Alleles: more than two alleles exist for a trait

Blood Type: Phenotype: Type A, AB, B, OGenotype: IAIA or IAi

IAIB IBIB or IBi

ii

Blood donation

clotting clotting

clotting clotting

clotting clotting clotting

Blood Type ExampleCross a heterozygous type A

mom with a Type O dad. What is the chance they have a child with Type O blood?

Sex Linked: trait found on the X sex chromosome

Phenotype: Female – less likely but can show a sex-linked trait

Genotype: XA XA, XA Xa , XaXa Phenotype: Male – sex-linked

traits show up more because they have XY sex chromosomes,

Genotype: XA Y, XaY No male carriers for a sex-linked trait

Sex-linked ExampleCross a colorblind dad with a

mom who is a carrier. What is the chance of this couple having a son who is not colorblind?

PolygeneticTraits that depend on many genes

and create a range of phenotypes.

Ex. Height, skin colorNO PUNNETT SQUARE!

Human skin colorAaBbCc x AaBbCc

◦can produce a wide range of shades

◦most children = intermediate skin color

◦some can be very light & very dark

Nature vs. Nurture:

Nature is heredity – your DNANurture is your environmentThe debate: Which has a greater

influence?Example: We use identical twins

to study the effects of the environment on genes.

Ticket Out the Door1. A sex-linked trait is found on

the __ chromosome.2. Cross a mom with type AB

blood with a dad who is type O. List all possible phenotypes.