Genetics - Week 1

Question 1

How many chromosomes are in the human genome?

Answer 1

• 23 different types of chromosomes
• diploid cells have two of each type (2n)

there are 46 total chromosomes

Question 2

How do different types of chromosomes differ?

Answer 2

• size
• shape
• location of centromeres
• genes

Question 3

What is an unreplicated chromosome?

Answer 3

each chromosome contains one double-stranded DNA molecule and one centromere

Question 4

What is a centromere?

Answer 4

specialized region of DNA that links sister chromatids, and also allows for proteins to bind during mitosis/meiosis

Question 5

What is a replicated chromosome?

Answer 5

each chromosome contains two identical double-stranded DNA molecules, aka two sister chromatids

Question 6

How many centromeres are on each chromosome?

Answer 6

whether replicated or unreplicated, each chromosome has only one centromere

of centromeres = # of chromosomes

Question 7

When is DNA tightly coiled and bunched?

Answer 7

when chromosomes are in their condensed form

Question 8

What are sister chromatids?

Answer 8

two identical double-stranded DNA molecules

- have identical sequences

Question 9

What are alleles?

Answer 9

genetic variants of genes

Question 10

What is a chromosome?

Answer 10

condensed DNA + proteins

Question 11

What is a chromatid?

Answer 11

one uninterrupted DNA molecule + associated proteins

• used to describe chromosomes only when there are 2 DNA molecules (sister chromatids)
• however you can think of a single chromatids as a single DNA molecule

Question 12

What is a haploid (n) cell?

Answer 12

has one of each type of chromosome

of chromosomes = n

Question 13

What is a diploid (2n) cell?

Answer 13

has two of each type of chromosome

of chromosomes = 2n

Question 14

How many chromosomes do we usually see in species with polyploidy?

Answer 14

even numbers of chromosomes

Question 15

What is polyploidy?

Answer 15

more than two copies of each chromosome

Question 16

What is a karyotype?

Answer 16

picture of an individual’s chromosomes

Question 17

Describe how ploidy level varies between species.

Answer 17

• many organisms (ie. mushroom, yeast) take a haploid form during all or part of their life cycle
• in some cases, the extra sets of chromosomes can make the organism more robust than it would be otherwise
• an odd number of chromosomes, however, often leads to sterility and abnormalities

Question 18

What is a genome?

Answer 18

all of the DNA in a cell

Question 19

Describe the female and male genomes.

Answer 19

• females have a bigger diploid genome than males in humans
• females have X chromosomes
• males have Y chromosomes

Question 20

What is the genome of the plant cell?

Answer 20

nuclear + mitochondrial + chloroplast genomes

Question 21

What is the genome of the animal cell?

Answer 21

nuclear + mitochondrial genome

Question 22

What is the genome of the prokaryotic cell?

Answer 22

genome (in nucleoid)

Question 23

What is the mitochondrial genome?

Answer 23

• human mitochondrial genome is distinctly different from that of the nuclear genome
• contained in a single, circular chromosome (similar to most bacteria)
• in humans (and most other species), mitochondria are normally inherited exclusively from the mother
• variable in size

Question 24

What is the chloroplast genome?

Answer 24

• photosynthetic organisms (ie. plants, algae, cyanobacteria) will have an additional distinct genome called the chloroplast genome
• circular in nature (similar to most bacteria)

Question 25

What is the nuclear genome?

Answer 25

• composed of linear DNA molecules

- in humans, these are organized as 46 linear chromosomes inherited from two parents

Question 26

What is a gene?

Answer 26

specific region of a chromosome which encodes (contains the DNA sequence information for making) a functional RNA molecule or protein molecule

Question 27

What is transcription?

Answer 27

DNA to RNA

Question 28

What is translation?

Answer 28

RNA to protein

Question 29

Describe the relationship between number of genes and genome size.

Answer 29

number of genes in a genome cannot be predicted based on genome size

Question 30

Describe the differences in different genomes.

Answer 30

• can vary widely in the proportion of genes to non-coding DNA
• can be tightly packed or widely dispersed

Question 31

Describe the relationship between complexity (# of cells) and genome size.

Answer 31

complexity (# of cells) of the organism does not correlate to its genome size