Introduction to Mendel and the Gene

Question 1

What did Mendel work with to figure out the rules of inheritance?

Answer 1

garden peas

Question 2

What is blending inheritance?

Answer 2

parental traits blend; offspring have intermediate traits
Black sheep + white sheep = gray sheep

Question 3

​What is Inheritance of acquired characteristics?

Answer 3

parental traits are modified through use and passed on
- Giraffes stretch their necks, offspring end up with longer necks

Question 4

Why did garden peas make a good model organism for Mendel’s work?

Answer 4

a species used for research
Practical to work with
Conclusions drawn from them can be applied to other species
They have several polymorphic traits
inexpensive
easy to grow
short generation time

Question 5

How did Mendel control mating in his pea experiments?

Answer 5

Peas normally self-fertilize (self-pollinate) so Mendel prevented self-pollination by removing the male organs from a flower before pollen formed
he used cross-pollination

Question 6

What is cross pollination?

Answer 6

It collects pollen from one individual and transfers it to the female organ on another plant whose male organs have been removed

Question 7

What traits did Mendel study?

Answer 7

seven traits and each of the traits had two distinct phenotypes

Question 8

What were the seven traits?

Answer 8

Seed shape
Seed color
Flower color
Flower position
Plant height
Pod shape
Pod color

Question 9

What is a reciprocal cross?

Answer 9

To determine if biological sex (male vs. female) influenced inheritance, Mendel performed a reciprocal cross
Mother’s phenotype in 1st cross is father’s phenotype in 2nd cross
Father’s phenotype in 1st cross is mother’s phenotype in 2nd cross

Question 10

What is the law of segregation?

Answer 10

Segregate into different gamete cells during the formation of eggs and sperm in the parents
happens in meiosis I

Question 11

What is the law of independent assortment?

Answer 11

alleles of different genes are transmitted independently of each other
four possible phenotypes should be shown in a 9:3:3:1 ratio

Question 12

What is sex-linked inheritance?

Answer 12

occurs when a gene is located on a sex chromosome

Question 13

What is autosomal inheritance?

Answer 13

occurs with genes on non-sex chromosomes

Question 14

What is codominance?

Answer 14

Neither allele is dominant or recessive to the other
ex: ABO blood types

Question 15

Incomplete dominance?

Answer 15

Heterozygotes have an intermediate phenotype
pure-line plants with red flowers (RR) crossed to pure-line plants with white flowers (rr) : Rr phenotype is a pink flower

Question 16

How can the environment influence a phenotype?

Answer 16

with diet, temperature, oxygen levels, humidity, light cycle, lack of nutrients, and mutagens can all affect an organism

Question 17

Example of environment influencing a phenotype

Answer 17

The human genetic disease phenylketonuria (PKU) is an example of a gene-by-environment interaction:
-Individuals with PKU are homozygous recessive for a gene that codes for an enzyme
Individuals placed on a low-phenylalanine diet develop

Question 18

What are examples of quantitative traits?

Answer 18

human height and skin color

Question 19

What is a quantitative trait?

Answer 19

a trait that varies continuously

Question 20

What is a pedigree?

Answer 20

a family tree that is used to learn the mode of transmission for a given trait

Question 21

What is an autosomal recessive trait?

Answer 21

is the phenotype is due to this, Individuals with the trait must be homozygous (i.e. ss) example: sickle cell disease
Unaffected parents of an affected individual:
Are likely to be heterozygous for the trait (i.e. Ss

Question 22

Autosomal dominant trait?

Answer 22

Homozygous (HH) or heterozygous (Hh) individuals will display the trait
One heterozygous parent will pass it on to about half of his/or her offspring (kids are Hh or hh)
example: Huntington disease

Question 23

What are X-linked recessive traits?

Answer 23

X-linked recessive traits are common
Men (XY) will exhibit the trait if they inherit it from their mothers
Women (XX) will exhibit the trait only if they are homozygous
Usually skips a generation
example: red-green colorblindness

Question 24

What are X-linked dominant traits?

Answer 24

X-linked dominant traits are rare
An affected male passes the trait to all his daughters but none of his sons
Daughters receive his only X chromosome
A female carrier will pass the trait to half her daughters and half her sons
Both sexes receive one of her X chromosomes

Question 25

Mendel’s principle of segregation reflects what event in meiosis?

Answer 25

separation of homologous chromosomes at
meiosis I

Question 26

Alternative versions of individual genes are called
________.

Answer 26

alleles

Question 27

Red–green color blindness is caused by a recessive allele on the X chromosome. A female with normal vision whose father is colorblind marries a colorblind male. What is the probability that a son of this couple will be colorblind?


Answer 27

0.5

Question 28

A cross between a black mouse and a brown mouse produced 4 black offspring and 4 brown offspring. Black coat color is dominant to brown coat color, and therefore you can conclude that ________.

Answer 28

the black parent was heterozygous

Question 29

What is the probability of getting exactly two recessive traits in offspring of a cross between two parents with genotypes of AaBbCc?


Answer 29

3/16

Question 30

Which of the following is the chromosome composition of men?

Answer 30

44 autosomes + XY

Question 31

Goltz syndrome is a rare genetic disorder that causes skin abnormalities. If a man with Goltz syndrome marries an unaffected woman, all of their daughters, but none of their sons, will have the disorder. Therefore, this disorder is _____.

Answer 31

dominant X-linked