Mendelian Genetics

Question 1

What did Mendelian study?

Answer 1

pea plants

Question 2

Why did Mendelian study peas?

Answer 2

they have short generation time, produce a large number of offspring

Question 3

What is hybridization?

Answer 3

The cross-breeding of organisms with certain traits to obtain other specific traits

Question 4

What is a gene?

Answer 4

-genes are alternative versions of traits
-genes are made up of DNA
-multiple genes make up a chromosome
-a gene is the basic functional unit of heredity

Question 5

What is an allele

Answer 5

-An allele is 1 of 2 or more alternative forms of a gene
-dominant alleles mask the recessive alleles (determines the characteristic)
-2 alleles separate during gamete formation and end up in different gametes

Question 6

What is a phenotype?

Answer 6

a phenotype is an observable expression of a heritable trait ex) color

Question 7

What is a genotype?

Answer 7

a genotype is the pattern of heritable alleles ex) PP - homozygous

Question 8

What is Pp an example of

Answer 8

heterozygous genotype

Question 9

What is ‘nn’ an example of

Answer 9

homozygous genotype

Question 10

What is a test cross?

Answer 10

-A test cross can be used when dealing with an unknown genotype
-the genotype can be characterized by a test cross with a known recessive genotype

Question 11

What are Mendel’s Laws?

Answer 11

1. Law of segregation
2. Law of independent assortment

Question 12

What is the Law of segregation?

Answer 12

Law of segregation is when 2 alleles separate during gamete formation and end up in separate gametes.

Question 13

What is the law of independent assortment?

Answer 13

Law of independent assortment is when each pair of alleles separate independently from any other pair or alleles during gamete formation
-applies to genes that are located on different chromosomes

Question 14

What does Mendel’s laws assume?

Answer 14

simple inheritance:
-each character is described by 1 gene
-each gene has 2 alleles
-each gene has 1 complete dominant and 1 complete recessive
-each gene is located on a separate chromosome

Question 15

What are the degrees of dominance?

Answer 15

Incomplete dominance and codominance

Question 16

What is incomplete dominance?

Answer 16

when neither allele dominates

Question 17

What is codominance?

Answer 17

when 2 alleles affect the phenotype in separate distinguishable ways
-ex) human blood

Question 18

Enzymes in Mendel’s peas

Answer 18

R = correct enzyme
r = defective enzyme
rr = peas accumulate excess unbranched starch that causes osmotic swelling and wrinkling when dry

Question 19

What is pleiotropy?

Answer 19

when one gene produces multiple phenotypes
-ex) pea gene for the flower color also determines the color of the seed coating

Question 20

What is epistasis?

Answer 20

When the phenotypic expression of 1 gene affects the phenotypic expression of another gene
-ex) Labrador coat color

Question 21

What is polygenic inheritance?

Answer 21

when 1 phenotype is affected by multiple genes
-ex) height, skin color

Question 22

What is meiosis?

Answer 22

-ensures that daughter cells inherit different genetic material than parent cells
-consists of 2 consecutive rounds of cell division
1. separates homologous chromosomes into separate cells
2. separates each sister chromatid to produce a haploid gamete

Question 23

What are chromosomes?

Answer 23

-cellular structures that consist of genes
-follow Mendel’s laws of segregation and independent assortment during meiosis
-Thomas H Morgan showed that they carry genes

Question 24

What did Thomas H Morgan study?

Answer 24

Drosophila (fruit flies)

Question 25

What are sex-linked genes?

Answer 25

-sex linked genes are found on sex chromosomes
-show altered inheritance patterns from autosomal genes

Question 26

What are sex chromosomes?

Answer 26

-determine the sex of the offspring depending on what is passed down
-XX = girl
-XY = boy
-Y can only be passed onto offspring from male

Question 27

Describe linkages between chromosomes

Answer 27

-genes on the same chromosome tend to be inherited together (linked)
-when 2 genes are linked, their inheritance will assort dependently

Question 28

Describe recombination

Answer 28

-during meiosis, homologous chromosomes can break and recombine from crossovers

Question 29

What affects the recombination frequency?

Answer 29

the physical distance on the chromosomes