bio monohybrid and terminology quiz

genetics

the branch of biology that studies heredity

• history -- pangenesis (suggested by hippocrates) -- blending hypothesis -- T.A. Knight (garden peas)

pangenesis

suggested by hippocrates

• particles called "pangenes" travel from each part of the body to sperm or egg cell

• implies that acquired characteristics can be passed on

pangenes

particles from each parts of the body that travel to sperm or egg cells

blending hypothesis

• idea that traits from each parent blend together (like paint)

• did NOT explain why traits not present in one generation reappear in later ones

t.a. knight

• conducted early experiments with garden peas

• said that one color had a stronger tendency to appear than others

gregor mendel

• called the "father of modern genetics" -- lived in a monastery

• repeated knight's experiments, but in a more scientific fashion

mendel's reasons for pea plant

1. many varieties

2. always showed one of two forms of a trait

3. small and easy to grow

4. mature quickly and produce many offspring

5. male and female reproductive on the same flower

6. can self-pollinate or cross-pollinate

mendel's laws

1. law of dominance and recessiveness

2. law of segregation

3. law of independant assortment

law of dominance and recessiveness

says that dominant traits can mask or hide the other recessive traits

• dominant traits - capital letter

• recessive traits - lowercase letter

dominant trait

capital letter

recessive trait

lowercase letter

law of segregation

says that each parent only passes on one allele (form of a gene) to their offspring

law of independent assortment

says that just because you are dominant for one trait does not mean you are dominant for all traits (alleles for different characteristics assort independently of each other)

allele

alternative form of a specific gene
- ex: allele for eye colors: blue, green, brown

mendel's experiments

1. first he grew plants that were pure for a trait by allowing them to self-pollinate

• only produced offspring with that trait

• ex: either all tall or all short

2. next he crossed two plants who were pure for different forms of the trait

• ex: crossed a pure tall plant w/ a pure short

• result: all showed dominant trait (tall) - F1 generation

3. finally he allowed the plants from the F1 generation to self-pollinate, producing the F2 generation

• in the f2 generation 3/4 of the plants showed the dominant trait and 1/4 showed recessive

• ex: 3/4 tall, 1/4 short

pure for a trait

ex TT (x) TT or tt (x) tt

gene

a segment of DNA that controls a particular trait
- p53; any gene (eye color, skin color)

homozygous

both alleles (letters) for a trait are alike

• you inherited the same alleles (letters) from both parents

• ex: TT, tt, AA, aa

heterozygous

alleles (letters) for a trait are different

• you inherited different alleles (letters) from both parents

• ex: Tt, Aa

genotype

genetic makeup of an individual; letters
- ex: Tt, BB, cc

phenotype

the appearance of an organism based on the genotype; words
- ex: brown, tall, blue, short

probability

percent chance that you would expect of an occurence

monohybrid cross

crosses that involve only one of 2 forms of a trait
- involves using a punnett square

review question 11/10/22

in a punnett square, how many homozygous recessive representatives are there always?
- on group of 2 lowercase