College Biology - Genetics Unit

Test 5

Gregor Mendel (Father of Genetics)

• Come in pairs

• Retain characteristics through generations

• Separate in gamete formation

Pisum Sativum

• The perfect species for studying genetics

  • Control characteristics

  • 7 characters each with 2 traits

  • Traits either completely dominant or recessive

    • Self pollinate or cross pollinate

Genotype

Genetic Makeup [RR, Rr, rr]

Phenotype

Physical physiological makeup [example: round or wrinkled]

Mendel’s Experiments

Started with true breeding plants

• P and F1

What is “P”

Parent generation

What is “F1”

First filial (generation)

• 1st born

Mendel learned…

There is no blending of traits!

Alleles

The pair that traits come in

Law of Segregation

Alleles separate during gamete formation

• Meiosis - one from each parents

How Mendel’s Experiment Worked

What is a punnett square?

A square diagram that is used to predict the genotypes of a particular cross or breeding experiment

Monohybrid Punnett Square Example

Dihybrid Cross - what did Mendel find out?

Similar ratios when he crossed single traits and double traits: therefore…

One trait DOES NOT affect the other.

Law of Independent Assortment

During gamete formations gene pairs assort independently of one another

Dihybrid Punnett - Steps

1. Write down genotype of parents

2. Make two separate monohybrid punnett squares

3. Jot down ALL phenotypes

4. Find ratios of all by multiplying

Dihybrid Punnett Square Example - from my notes

Note: it is the same process for Trihybrid crosses and more

Incomplete Dominance + Example

Heterozygous is intermediate between homozygous phenotypes

• Middle

Codominance + Example

Heterozgous shows BOTH phenotypes of different alleles

• Co = blended

Multiple Alleles + Example

More than 2 possible alleles for a trait

(One from mom, one from dad)

• Think blood types

RH Factor - key and what is it?

Positive or negative in a blood type

• (+) = dominant

• (-) = recessive

Genotype / Phenotype List for Blood

• AA - Type A

• AO - Type A

• BB - Type B

• BO - Type B

• AB - Type AB

• OO - Type O

Male vs Female

Male = XY

Female = XX

• Note: In X-linked, Y has no allele attached

X-Linked Recessive - key

X-Linked

A = normal

a = trait

X-Linked Dominant - key

X-Linked

A = trait

a = normal

Y-Linked

XY^A or XY^T

• A = normal

• T = trait

Pedigree - key

Square = male

Circle = female

Colored = trait

Pedigree - Example

Autosomal Dominant

Autosomal

A = trait

a = normal

Autosomal Recessive

Autosomal

A = normal

a = trait

Polygenic Traits

Many genes control 1 trait

• Shows continuous variation

• Must show a bell curve

Pleiotrophy (opposite of polygenic)

One gene having many effects

• Fragile x syndrome

• PKU

• Marfan syndrome

Epigenetics

External environmental influence that increases or decreases the chances of a gene being expressed

Gene Mapping

The process of determining the location of genes on chromosomes

Gene Mapping - Example