Introduction to Genetics Review (Exam Review #45-58 & #73-94)

Question 1

What is probability?

Answer 1

The likelihood of an event

Question 2

What is the probability of rolling 2 fours on a die in a row?

Answer 2

1/36

Question 3

What diagrams are used to show the possible gene combinations that could result from a genetic cross?

Answer 3

Punnett Squares

Question 4

What are organisms that have 2 identical alleles for the same trait called?

Answer 4

Homozygous

Question 5

What are organisms that have 2 different alleles for the same trait called?

Answer 5

Heterozygous

Question 6

What word is used to describe the physical characteristics of a genetic cross?

Answer 6

Phenotype

Question 7

What word is used to describe the genetic makeup of a genetic cross?

Answer 7

Genotype

Question 8

Draw a Punnett Square to show a cross between a heterozygous round seed and a wrinkled seed. (Round allele: R, Wrinkled allele: r) Give the possible genotypes and phenotypes and their percentages.

Answer 8

Genotypes:

Rr-50%

rr-50%

Phenotypes:

Round-50%

Wrinkled-50%

Question 9

Draw a Punnett Square to show a cross between a homozygous purple, heterozygous long-feathered Foo-Foo bird and a pink, short-feathered Foo-Foo bird. (P: purple, p: pink, L: long-feathered, l: short-feathered) Give the possible genotypes and phenotypes and their percentages.

Answer 9

PL Pl PL Pl

pl PpLl Ppll PpLl Ppll

pl PpLl Ppll PpLl Ppll

pl PpLl Ppll PpLl Ppll

pl PpLl Ppll PpLl Ppll

Genotypes:

PpLl-50%

Ppll-50%

Phenotypes:

Purple with long feathers-50%

Purple with short feathers-50%

Question 10

What is the law of independant assortment?

Answer 10

Alleles assort independently from one another.

Question 11

What happens in incomplete dominance?

Answer 11

The traits combine.

Question 12

Give an example of incomplete dominance.

Answer 12

A red flower and a blue flower have purple offspring

Question 13

What happens in codominance?

Answer 13

Both traits show through.

Question 14

Give an example of codominance.

Answer 14

A dog with a brown parent and a white parent has spots of both colors.

Question 15

What are traits that are controlled by two or more genes called?

Answer 15

Polygenic

Question 16

Genes that have more than two alleles are said to have what?

Answer 16

Multiple alleles

Question 17

The two chromosomes in a human that determine an individual’s sex are called what?

Answer 17

Sex chromosomes

Question 18

What is a pedigree?

Answer 18

A chart showing the appearance of a trait in a family

Question 19

Which pattern(s) of inheritance are consistent with this pedigree?

i. Sex-linked
ii. Complete dominance
iii. Cocominance

Answer 19

Complete dominance

Question 20

According to this pedigree, what is the best guess of the genotypes of the student’s parents?

Answer 20

Heterozygous

Question 21

According to the pedigree, what is(are) the most likely genotype(s) of the student’s sister?

Answer 21

WW or Ww

Question 22

Aside from genetics, what factor plays an important role in a person’s traits?

Answer 22

Environment

Question 23

What is the allele for Blood-type A?

Answer 23

I^A

Question 24

What is the allele for Blood-type B?

Answer 24

I^B

Question 25

What is the allele for Blood-type AB?

Answer 25

I^AI^B

Question 26

What is the allele for Blood-type O?

Answer 26

i

Question 27

List all the possible genotypes for Type-A blood.

Answer 27

I^AI^A and I^Ai

Question 28

List all the possible genotypes for Type-B blood.

Answer 28

I^BI^B and I^Bi

Question 29

List all the possible genotypes for Type-AB blood.

Answer 29

I^AI^B

Question 30

List all the possible genotypes for Type-O blood.

Answer 30

ii

Question 31

What is the dominant allele of the AB blood groups?

Answer 31

I^A and I^B

Question 32

What is the recessive allele of the AB blood groups?

Answer 32

i

Question 33

What is the dominant allele for the Rh blood group?

Answer 33

Rh⁺

Question 34

What is the recessive allele for the Rh blood group?

Answer 34

Rh^-

Question 35

A man heterozygous for type-A blood marries a woman heterozygous for type-B blood. What is the probability as a percentage that their child will have type-O blood? Hint: Use a Punnett Square

Answer 35

25%

Question 36

Name a disorder caused by a recessive allele.

Answer 36

Color-Blindness

Question 37

Name a disorder caused by a dominant allele.

Answer 37

Huntington's

Question 38

Name a trait controlled by codominant alleles.

Answer 38

Blood type

Question 39

In diseases like cystic fibrosis and sickl cell anemia, what causes the disorder?

Answer 39

A change in the DNA

Question 40

What are sex-linked genes?

Answer 40

Genes on the X or Y chromosome

Question 41

Give 2 examples of sex-linked disorders in humans.

Answer 41

Color-blindness and hemophilia

Question 42

In fruit flies, eye color is a sex-linked trait on the X-chromosome. If a female fruit fly heterozygous for red eyes (red eyes are dominant) is crossed with a white-eyed male (white eyes are recessive), what percentage of their offspring will have white eyes? Hint: use a Punnett Square

Answer 42

50% (remember that red eyes are X^R and white eyes are X^r)

Question 43

Why do males tend to have a higher probability of getting a sex-linked disorder than females?

Answer 43

They only have one X chromosome, and therefore only have one allele for each X-linked gene. That allele, being the only one, must show through.

Question 44

What is nondisjunction?

Answer 44

It occurs when homologous chromosomes fail to separate.

Question 45

Describe 2 chromosomal disorders.

Answer 45

Turner's: Only 1 X-chromosome Klinefelter's: 1 Y and too many X's

Question 46

What is DNA fingerprinting used for?

Answer 46

It is used to identify people.

Question 47

What is the purpose of the human genome project?

Answer 47

To map the human genome

Question 48

What is gene therapy?

Answer 48

Injecting a "good" gene to replace a "bad" one

Question 49

What are some ethical issues that can be raised with human genetics?

Answer 49

Answers may vary