Intro to Genetics. Genetics Student Expectation: B 6.F Predict possible outcomes of various genetic...

Intro to Genetics

Genetics

Student Expectation:

B 6.F

Predict possible outcomes of various genetic combinations such as

monohybrid crosses, dihybrid crosses and non-Mendelian inheritance.

Readiness Standard

Gregor Mendel

Austrian monk born 1822Lived in a monastery

and taught high schoolExperimented with pea plants by cross

breeding plants with different characteristics and studying results.

Known as the father of Genetics

Mendel’s Principles

Law of Inheritance – Characteristics or traits are inherited by individual units known as “genes”.

Vocabulary

Gene – the sequence of DNA that codes for a protein and thus determines a trait.

Example – a gene

will determine plant

height in peas.


Law of Segregation - states that during the formation of reproductive cells (gametes), pairs of hereditary factors (genes) for a specific trait separate so that offspring receive one factor from each parent.

Vocabulary

Allele – one of a number of different forms of a gene.

Example: this flower carries an allele for white and an allele for purple flowers


Law of Independent

Assortment - states

that chance deter-

mines which factor

for a particular trait

is inherited.


Law of Dominance – states that when 2 or more forms of a gene exist (alleles), some forms are dominant and others are recessive

Dominant/Recessive

Hitch Hikers Thumb Normal Thumb

Dominant/Recessive

Free Earlobes Attached Earlobes

Dominant/Recessive

Polydactyly is Dominant!!

Dominant/Recessive

Other examples of dominant traits:

Dimples

Tongue Rolling

Freckles

Curly hair (may be more than one gene)

Dominant/Recessive

Shapes for Pea seedsR = round (Dominant)r = wrinkled (recessive)

Genotype Phenotype RR Round homozygous dominant

Rr Round heterozygous dominant

rr wrinkled homozygous recessive

Monohybrid Crosses

Monohybrid Crosses

Practice some monohybrid crosses

BB x BBBB x BbBB x bbBb x BbBb x bb

What are the genotypic ratios?What are the phenotypic ratios?

Dihybrid Crosses

Non Mendelian Genetics

Exceptions to Mendel’s Principles:- Not all genes show simple patterns of

dominant and recessive alleles- The majority of genes have more than

two alleles.- Many traits are controlled by more than

one gene.


Incomplete Dominance - When one allele is not dominant over the other but the heterozygous offspring produce an intermediate (3rd) phenotype. Neither fully expressed.

Example:

Red (RR) x white (rr)

= Pink (Rr)


Co-dominance - Both alleles contribute to the phenotype. Both are expressed at the same time.

Example:Brown BB x White WW= brown and white - BW


Multiple Alleles - More than 2 possible alleles exist – not “either/or”. Only 2 expressed at a

time.

Example: Blood Type

iA, iB, iAiB, ii

Blood Type GenotypeCan Receive Blood From

AiAi = AOiAiA = AA

A or O

BiBi = BOiBiB = BB

B or O

AB iAiB A, B,AB, O

O ii = OO O

Multiple Alleles – Blood Types


Polygenic Traits - Traits controlled by several genes often on multiple chromosomes.

Examples:

Skin Color

Eye Color

Polygenic Traits

Skin Color


Sex Linked Traits -

Genes that are carried

by the sex chromosomes.

Read More: http://anthro.palomar.edu/biobasis/bio_4.htm

Journal Work

In your journal you will work the following punnett squares. This will be a graded assignment.

You must re-write or abbreviate the questions and you must show your work and circle or hi-lite your answers.

Journal Work Problem 1

Identify each of the following as: Homozygous dominant, homozygous recessive or heterozygous.

A. bb B. HybridC. TTD. GgE. Purebred

Journal Work - Problem 2

Dominant/Recessive Monohybrid Cross

Draw a Punnett square and provide the genotypic and phenotypic information.I = Not allergic to Iodine i – allergic to iodine

Ii x II Genotypic ratios Phenotypic ratios

Ii x ii Genotypic ratios Phenotypic ratios



Two elephants are crossed and the resulting offspring have 50% large ears and 50% small ears.

E = large ears e = small ears

What are the genotypes of the parent?

SHOW YOUR PUNNETT SQUARE.



A black rabbit is crossed with a white rabbit. 100% of the offspring are heterozygous for color.

B = black b = whiteWhat are the genotypes of the parent?

What are the phenotype percents for the offspring?

SHOW YOUR PUNNETT SQUARE.



Cross a homozygous fuzzy bear with a hairless bear.

F = fuzzy f – hairless

What are the F1 genotypic ratios?

What are the F1 phenotypic ratios?



Cross a heterozygous purple-flowered plant with a plant that has white flowers.

P = purple p – white

What are the F1 genotypic ratios? What are the F1 phenotypic ratios?

Journal Work – Problem 7

Dominant/Recessive Dihybrid Cross:

Y – yellow peas P – purple flowers T-tall planty – green peas p – white flowers t – short plant

Cross two heterozygous tall, heterozygous yellow pea plants.

What are the parent genotypes?




Y – yellow peas P – purple flowers T-tall planty – green peas p – white flower t – short plant

Cross a short, purple flower plant that is homozygous for color with a short, purple flower plant that is heterozygous for color.

Whate are the parent genotypes?




Y – yellow peas P – purple flowers T-tall planty – green peas p – white flower t – short plant

Cross a heterozygous purple flowered, green pea plant with a plant that has white flowers and is heterozygous for pea color.




Incomplete Dominance - Monohybrid Cross:In snapdragons, red and white are both dominant.

When they cross, they produce a pink flower.

R – red R’ – white

Cross a homozygous red and a homozygous whitesnapdragon.




Co - Dominance - Monohybrid Cross:

In a certain type of chicken, black and white feather share dominance. When they cross they produce chickens with both black and white feathers.

B - black B’ - white

Cross a homozygous black and a homozygous white chicken.




Incomplete and Co - Dominance - Dihybrid Cross:

In Fuzzy Trolls, Blue and Purple hair are both dominant. A hybrid genotype produces blue and purple stripes. Yellow skin and Red skin are both dominant. A hybrid genotype produces orange skin.

B – Blue hair Y – yellow skin B’ – Purple hair Y’ Red skin

A troll with purple hair and red skin reproduces with a troll with blue hair and orange skin.




Multiple Alleles Monohybrid Cross:

Blood Type: Cross a heterozygous Type A with a heterozygous Type B.



Blood Type GenotypeCan Receive Blood From

AiAi = AOiAiA = AA

A or O

BiBi = BOiBiB = BB

B or O

AB iAiB A, B,AB, O

O ii = OO O


Sex Linked - Monohybrid Cross:

A female who is a carrier for baldness marries a man with normal hair patterns

H – Normal hair pattern h – bald



Intro to Genetics. Genetics Student Expectation: B 6.F Predict possible outcomes of various genetic...

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