Unit 5: Inheritance Patterns

Question 1

Genetics:

Answer 1

-science that deals with heredity and variation.

Question 2

Heredity:

Answer 2

-passing of traits from one generation to the next.

Question 3

Traits are either:

Answer 3

•inherited: passed on from family.
•acquired traits: from environment, not passed on.

Question 4

Alleles:

Answer 4

•versions of a gene.
•one from each parent.
-ex: gene- height
—alleles- Tall or short.
•dominant or recessive:
-Tall: dominant (T).
-Short: recessive (t).

-allele—> 1 letter.

Question 5

Homozygous:

Answer 5

•2 copies of the same allele.
•ex: TT or tt.

Question 6

Heterozygous:

Answer 6

•two different alleles for a gene.
•AKA: carrier (heterozygous).
-ex: Tt.

Question 7

Genotype:

Answer 7

-genetic make-up of an individual.
-ex: TT, Tt or tt.

Question 8

Phenotype:

Answer 8

-what is seen, physical expression of a gene.
-ex: tall or short.

Question 9

History of genetic (Gregor Mendel):

Answer 9

•Austrian monk (1822-1884).
•worked with garden peas because:
1. Can grow large numbers.
2. Can cross or self pollinate plants.
3. Distinct traits. (Ex: either purple or white flowers not a mauve!)
•father of genetics.

Question 10

Mendel’s laws:

Answer 10

1. Law of dominance.
2. Law of segregation.
3. Law of independent assortment.

Question 11

1. Law of dominance:

Answer 11

•traits are controlled by a pair of factors (alleles).
•one factor can mask (dominance) the other (recessive).

Question 12

2. Law of segregation:

Answer 12

•all individuals have two copies of a gene. These copies segregate during gamete formation. Each gamete receives one copy of each gene.

Question 13

3. Law of independent assortment:

Answer 13

•two alleles for one gene segregate (assort) independently of the alleles for other genes during gamete formation.

Question 14

Punnet squares:

Answer 14

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

Question 15

Test cross:

Answer 15

•to determine an unknown dominance genotype:
-cross with a known: homozygous recessive.
-results:
•homozygous dominant: all dominance offspring.
•heterozygous: 1/2 dominant, 1/2 recessive.

•done when you know the phenotypes of the offspring, but you don’t know the genotypes of the parents.
•the cross of an individual of unknown genotype to an individual that is fully recessive.
•it helps us determine if the unknown is homozygous or heterozygous for the dominant allele.

Question 16

P generation:

Answer 16

-parents.

Question 17

F1 generation:

Answer 17

-children of the P generation.

Question 18

F2 generation:

Answer 18

-children of the F1 generation.
-P generation would be their grandparents.

Question 19

Other patterns of inheritance:

Answer 19

1. Multiple alleles.
2. Incomplete dominance.
3. Co-dominance.

Question 20

1. Multiple alleles:

Answer 20

•genes that have more than two forms.
•use capital letters with superscript numbers or letters.
•humans: one gene for ABO blood type:
-I^A, I^B, or I^O (i).

•fruit fly (drosophila melanogaster) has many alleles for eye color:
-E^1 is wild type (dominant); E^2 is apricot; E^3 is honey; E^4 is white (recessive).

•multiple alleles- blood types:
A= I^A I^A or I^A i
B= I^B I^B or I^B i
AB= I^A I^B
O= ii
•alleles I^A and I^B are co-dominant to one another, but both are dominant over allele i (order of dominance).

Question 21

2. Incomplete dominance:

Answer 21

•when two alleles are equally dominant.
•they interact to form a new phenotype.
•THINK- RED + WHITE = PINK.
•offspring expresses a trait as a combination of both parents.
•use upper case letter with a number (R1 or R(prime)) or superscripts.
•human examples:
-sickle cell anemia.

Question 22

3. Co-dominance:

Answer 22

•when both alleles are expressed fully in different cells (see both traits independently).
•THINK- RED + WHITE = RED + WHITE.

Question 23

Roan:

Answer 23

-a mix of red and white.

Question 24

Dihybrid crosses:

Answer 24

•cross involving two independent traits present in alternate forms.
•independent traits are found on DIFFERENT chromosomes.

Question 25

Crossing more than one trait…

Answer 25

•dihybrid: crossing 2 traits. •trihybrid: crossing 3 traits.

Question 26

For dihybrid remember this: BOTH PARENT HETEROZYGOUS (for both traits) (!PHENOTYPE!) RATIO:

Answer 26

•Ex: RrYy x RrYy. •RY, Ry, rY, ry: •9:3:3:1. ^phenotype ratio! (Only works for traits found on different chromosomes).

Question 27

Polygenic inheritance:

Answer 27

•trait controlled by two or more genes. •continuous traits: height, skin and eye color. •each can have multiple alleles, show incomplete or co-dominance, and can be affected by environment. •makes breeding for these traits very difficult.

Question 28

Epistatic traits:

Answer 28

•epistatic traits: a gene that masks the expression of another gene or genes. •ex: coat color in dogs. The gene responsible for albinism is epistatic. The gene interferes with the expression of genes that determine pigment formation. •B= black, b= brown, W= albinism (prevents formation of pigment), w= allows pigmentation. •example: wwBb = black, WwBb = white (albino). The W allele masks the effect of the B colour gene. •more examples: -BbWw: albinism (no pigment). -bbww: brown. -bbWw: albinism (no pigment). -BBWw: albinism (no pigment).

Question 29

Remember you always get one ______ from mom and one from dad to create a genotype.

Answer 29

-allele.

Question 30

Selective breeding:

Answer 30

•for a desirable trait or eliminate undesirable. •offspring are homozygous for most traits. •can be achieved by mating closely related individuals (inbreeding).

Question 31

Hybrids (plants):

Answer 31

•from mating parents with different forms of a trait. •usually results in larger and stronger plants. •example: disease resistant plant crossed with plant that produces larger and more numerous fruit—> offspring plants are disease resistant and produce a lot of fruit.

Question 32

Environmental influence:

Answer 32

•temperature, nutrition, light and chemicals can all influence gene expression. •sex can affect expression as well.