Mendel and The Gene

Question 1

What was used to explain Mendel’s results?

Answer 1

Chromosomal theory of inheritance

Question 2

What process was Mendel seeing in action, that led him to his observations?

Answer 2

Meiosis

Question 3

What did Mendel find to be “hereditary determinants”?

Answer 3

Genes located on chromosomes

Question 4

What undergoes segregation and independent assortment: chromosomes or individual genes?

Answer 4

Chromosomes

Question 5

Why are flies a great subject for genetic research?

Answer 5

• Produce tons of offspring
• Can breed a new generation every 2 weeks
• only 4 pairs of chromosomes
• cheap to keep

Question 6

Where is the eye color gene located in fruit flies?

Answer 6

On the sex chromosome (they are linked)

Question 7

What is sex-linked inheritance?

Answer 7

Genes located on a sex chromosome that exhibit unique patterns of inheritance

Question 8

What is used to determine sex in humans and other mammals?

Answer 8

The X-Y system

Question 9

X & Y chromosomes segregated into separate gametes (sperm) during meiosis in males leads to what?

Answer 9

Sex determination

Question 10

What is the sex if an X-bearing sperm fertilizes an egg?

Answer 10

Female

Question 11

What is the sex if a Y-bearing sperm fertilizes an egg?

Answer 11

Male

Question 12

Before 2 months, the embryo’s gonads are generic and can develop into ovaries or testes depending on what?

Answer 12

The presence of the Y chromosome

Question 13

What happens with the gonads if the Y chromosome is expressed?

Answer 13

They develop into testes

Question 14

How many genes does the Y chromosome contain?

Answer 14

78 (encodes 25 proteins)

Question 15

How many genes does the X chromosome contain?

Answer 15

~1,100

Question 16

Why are there fewer disorders passed from father to son?

Answer 16

There are less genes in the Y chromosome

Question 17

True/False: XY is always phenotypically male.

Answer 17

False (can be phenotypically female)

Question 18

True/False: XX can be phenotypically male.

Answer 18

True

Question 19

What causes XY to be phenotypically female?

Answer 19

Loss of SRY gene

Question 20

What causes XX to be phenotypically male?

Answer 20

Translocation of SRY gene

Question 21

What is the SRY gene?

Answer 21

It provides the instructions for making the sex-determining region Y protein

Question 22

Why are X-linked recessive disorders more common in males than females?

Answer 22

Males only have 1 X chromosome, which means that they can not be carriers of the disorder. They either have it or they don’t. Females have 2 X chromosomes which means that one good copy of the X can mask the bad copy of the X and therefore be just a carrier.

Question 23

What are some X-linked disorders?

Answer 23

• Color blindness
• Duchenne muscular dystrophy
• Hemophilia

Question 24

True/False: All alleles are either completely dominant or completely recessive.

Answer 24

False

Question 25

True/False: Some genes have more than 2 possible alleles.

Answer 25

True

Question 26

True/False: Genes can not produce multiple phenotypes.

Answer 26

False

Question 27

Because it is unlikely for genes on the same chromosome to sort independently, would you expect them to stay together during gamete production?

Answer 27

Yes

Question 28

What is the term used to describe offspring that do not have phenotypes that match either parent?

Answer 28

Recombinants

Question 29

What is the cause of recombinant cases?

Answer 29

Crossing over

Question 30

What increases the chance of a crossover event?

Answer 30

The farther apart 2 genes are on a chromosome

Question 31

What type of phenotype do heterozygotes have in the case of incomplete dominance?

Answer 31

Intermediate phenotype

Question 32

What does it mean when alleles are co-dominant?

Answer 32

Neither allele is dominant and both are expressed with no blending

Question 33

What is a heterozygote?

Answer 33

An individual having 2 different alleles of a particular gene or genes

Question 34

What is the flaw with Mendel only looking at characters which had 2 alleles?

Answer 34

Most genes have more than 2 alleles which allows for more combinations, which means more phenotypes

Question 35

What is pleiotropy?

Answer 35

A specific gene that produces multiple traits

Question 36

What is the term used to describe when the phenotypic expression of one gene alters that of a different gene?

Answer 36

Epistasis

Question 37

What is the term used to describe when 2 or more genes have an additive effect on a single phenotypic character?

Answer 37

Polygenic Inheritance

Question 38

True/False: The phenotype of many traits can be altered or influenced by the environment

Answer 38

True

Question 39

Both parents must be at least a carrier for what?

Answer 39

Recessively inherited disorders

Question 40

True/False: Dominantly inherited disorders can skip generations.

Answer 40

False

Question 41

True/False: Recessively inherited disorders can skip generations.

Answer 41

True