Exam 4: Chapters 11 And 12

Question 1

Allele

Answer 1

Alternate versions of the same gene; different nucleotide sequence

Question 2

Diploid

Answer 2

Having 2 sets of genes (two copies of each chromosome) (humans are diploid organisms)

Question 3

Haploid

Answer 3

Having only one set of genes (one copy of each chromosome)(human gametes are haploid)

Question 4

Gametes

Answer 4

Haploid reproductive or sex cells (sperm or egg in humans)

Question 5

Zygote

Answer 5

First haploid cell of new generation, develops by mitosis into an embryo

Question 6

Genotype

Answer 6

An organism’s genetic makeup (alleles you have)

Question 7

Phenotype

Answer 7

Physical or observable features

Question 8

Homozygous

Answer 8

Having 2 identical alleles

homo=“same”, AA or aa

Question 9

Heterozygous

Answer 9

Having 2 different alleles of a gene (hetero=“other” Aa)

Question 10

Dominant

Answer 10

Determines phenotype if present in 1 or 2 copies (uppercase letter)

Question 11

Recessive

Answer 11

Affects phenotype only if 2 copies are present, masked by dominant if present in 1 copy only (lowercase letter)

Question 12

Carrier

Answer 12

Individual who have one copy of the recessive allele but appeal normal are carriers of the disorder (heterozygotes)

Question 13

Autosomal vs. sex linked traits

Answer 13

Sex linked: (man / woman)
(Woman: XX)
(Man: XY)

Autosomal: both men and women receive the same traits/genes

Question 14

Nondisjunction

Answer 14

Failure of chromosomes to separate during cell division

Question 15

What does it mean to say they carry equivalent genes?

Answer 15

?

Question 16

How many genes chromosomes are in human gametes

Answer 16

23

Question 17

Meiosis involves ________ of cell division

Answer 17

A special type of cell division producing genetically diverse gametes

Question 18

In which phase of meiosis I or II does each of the following occur
(specify prophase I, metaphase II, anaphase III, telophase IIII)

A. Sister chromatids begin moving to opposite poles

Answer 18

Anaphase II

Question 19

In which phase of meiosis I or II does each of the following occur
(specify prophase I, metaphase II, anaphase III, telophase IIII)

B. Recombination between homologous chromosomes

Answer 19

Prophase I

Question 20

In which phase of meiosis I or II does each of the following occur
(specify prophase I, metaphase II, anaphase III, telophase IIII)

C. Homologous pairs begins to separate

Answer 20

Anaphase I

Question 21

In which phase of meiosis I or II does each of the following occur
(specify prophase I, metaphase II, anaphase III, telophase IIII)

D. Cytokinesis begins, chromosomes are still doubled

Answer 21

Telophase I

Question 22

What are two sources of genetic variation in meiosis? Explain both.

Answer 22

• Recombination of homologous chromosomes

- Independant assortment (random lining up between chromosomes on the equator)

Question 23

Why and with what genotypes would you perform a testcross

Answer 23

• you do it when you have a dominant genotype cross it with a recessive genotype
• an individual of dominant phenotype (but unknown genotype)
• a homozygous recessive individual

Question 24

Why are genetic disorders NOT eliminated by natural selection? What is heterozygote advantage (give an example)

Answer 24

• heterozygous has a different genotype
• last onsetive disease
• medical advances

Question 25

How is gender determined in humans

Answer 25

Be the male (sperm)

Question 26

Does recombination occur between the X and Y chromosome? Why or why not

Answer 26

No because he Y is too short (not homologous) and it doesnt have enough information

(When maternal and paternal chromosomes pair and physically exchange DNA segments)

• the X chromosome
  (Woman: XX)
  ( Man: XY)

Question 27

Know the difference between complete dominance and incomplete dominance or co-dominance.

Answer 27

Ex: Red and White flower mix=
• complete dominance= dominant phenotype and recessive phenotype
• Incomplete dominance= when red and white mix, it equals the pink flower
• Codominance= red and white flower and blood type

Question 28

How do phenotypes and heterozygotes differ? Give an example of incomplete dominance and an example of codominance

ADD ANSWER TO FIRST QUESTION

Answer 28

Ex: Red and White flower mix=

• Incomplete dominance= when red and white mix, it equals the pink flower
• Codominance= red and white flower

Question 29

What is polygenic inheritance? Give 2 examples

Answer 29

A single trait determined by the interaction between alleles of more than one gene (more than one gene pair contributes to a single gene type)

Ex: human height (shows continuous variation)
: skin color
* continuous generation

Question 30

Give an example of a disorder caused by nondisjunction

Answer 30

Aneuploidy: an abnormal number of one or more chromosomes

Trisomy 21/Down Syndrome : risks of both increase maternal age

Question 31

When can nondisjunction happen

Answer 31

During meiosis produces aneuploid sperm and egg cells with too few or too many chromosomes

• Anaphase I
• Anaphase II