Chapter 2: The Human Genome and the Chromosomal Basis of Heredity

Question 1

hereditary material containing the genetic information

Answer 1

DNA

Question 2

• units of genetic information

- they are organized along the chromosomes with with precise location or locus

Answer 2

genes

Question 3

rod-shaped structures

Answer 3

chromsomes

Question 4

maps the chromosomal location of the genes

Answer 4

gene map

Question 5

species specific characteristic chromosome complement (number and morphology)

Answer 5

karyotype

Question 6

-study of chromosomal structure and inheritance

Answer 6

cytogenetics

Question 7

-normal human chromosome number is 46

Answer 7

nuclear genome

Question 8

-refers to all cells in the body except those of the

gamete-forming germline - most are diploid

Answer 8

Somatic Cells

Question 9

-members of a pair of chromosomes ->

carry same subset of genes arranged linearly along its DNA

Answer 9

Homologous chromosomes

Question 10

-one of the alternate versions of a gene or DNA sequence

at a given locus

Answer 10

alleles

Question 11

-located in the cytoplasm, have a small chromosome

which is an important part of the human genome

Answer 11

Mitochondria

Question 12

What is the length of the mitochondrial chromosome?

Answer 12

16kb, which is about 16,000 nucleotides

Question 13

• basic structural unit of chromatin

- appear as “beads on a string”

Answer 13

nucleosome

Question 14

• a secondary heliical chromatin structure of coiled nucleosomes appear as a thick 30-nm diameter cylindrical fiber

Answer 14

soleonoid

Question 15

What are the components that make up the DNA structure?

Answer 15

5-carbon deoxyribosenitrogen-containing purine (or pyrimidine base) phosphate group

Question 16

How is a nucleotide formed?

Answer 16

when a deoxyribose and a phosphate group join

Question 17

How may DNA molecules does the nuclear genome have?

Answer 17

46 DNA molecules

Question 18

Which histones can be post-translationally modified?

Answer 18

H3, H4

Question 19

What percentage do satellite DNA make up of all genetic material?

Answer 19

10-15%

Question 20

How do you find satellite DNA?

Answer 20

arrays of various short repeats organized tandemly head to tail

Question 21

different types of tandem repeats that can be separated as a distinct fraction of DNA

Answer 21

satellite DNA

Question 22

long arrays of satellite DNA found in genetically inert regions on chromosomes 1, 9, and 16 and more than one-half of the Y chromosome

Answer 22

pentanucleotide repeats

Question 23

What are 3 examples of dispersed repetitive DNA?

Answer 23

• Alu family
• LINE
• segmental duplications

Question 24

What is special about the Alu family?

Answer 24

it is the best studied dispersed repetitive element

Question 25

What is LINE?

Answer 25

a long interspersed nuclear element family composing ~20% of the genome. They are retrostransposons (copies can be integrated and cause insertional inactivation)

Question 26

What is segmental duplication?

Answer 26

genetic rearrangements that can lead to gene deletions resulting in disease

Question 27

Where does mitosis occur?

Answer 27

ordinary somatic cell division

Question 28

What does mitosis result in?

Answer 28

2 diploid daughter cells with 2n chromosomes identical to parent DNA

Question 29

Where does meiosis occur?

Answer 29

in germline cells

Question 30

What does meiosis result in?

Answer 30

in reproductive cell gametes that are haploid/contain 23 chromosomes

Question 31

What is interphase?

Answer 31

period of biosynthesis and growth between two mitosis; has 3 checkpoints

Question 32

What are the checkpoints of the cell cycle?

Answer 32

G1, G2, S phases

Question 33

When does G1 occur? is there synthesis of DNA?

Answer 33

after mitosis; no synthesis of DNA

Question 34

What happens in S phase?

Answer 34

chromosomes replicate to become bipartite with 2 sister chromatids

Question 35

What are telomeres?

Answer 35

in the end of each chromatid, they ensure chromosome integrity during cell division

Question 36

What is telomerase?

Answer 36

enzyme that maintains chromosome ends

Question 37

What does it mean that DNA replication is a semiconservative process?

Answer 37

it means that one strand of the double helix is directly from the parent and the other is synthesized from that

Question 38

What does the centromere do?

Answer 38

it holds the two sister chromatids together

Question 39

during what phase do chromosomes start to condense?

Answer 39

mitotic phase (M phase)

Question 40

What happens in M phase?

Answer 40

chromosomes condense and 1 chromatid of each chromosome is distributed to each daughter cell

Question 41

What are the 5 stages of Mitosis?

Answer 41

Prophase, Prometaphase, Metaphase, Anaphase, Telophase

Question 42

What happens in prophase?

Answer 42

chromosomal condensation and formation of mitotic spindle

Question 43

What happens in prometaphase?

Answer 43

nuclear membrane breaks up, chromosomes attach to microtubule in kinetochore

Question 44

What happens in metaphase?

Answer 44

maximum condensation and alignment at equatorial plane

Question 45

What happens in anaphase?

Answer 45

chromsomes separate at centromere, sister chromatids separate and are independent daughter chromosomes, they move to opposing poles

Question 46

What happens in telophase?

Answer 46

chromosomes begin to decondense, nuclear membrane begins to form

Question 47

What is euchromatin?

Answer 47

It is the C-G rich portion of chromatin; it is genetically active

Question 48

What is heterochromatin?

Answer 48

chromosomal segment that remains in interphase is mostly repetitive DNA with no genetic activity

Question 49

What are the phases of Prometaphase in Meiosis 1?

Answer 49

Leptotene, Zygotene, Pachytene, Diplotene, Diakenesis

Question 50

What are the consequences of Meiosis?

Answer 50

1) reduction of chromosome number from diploid to haploid 2) shuffling of genetic material due to random assortment of the homologues 3) additional shuffling of genetic material due to crossing over

Question 51

What is G-banding?

Answer 51

technique used to stain chromosomes; it shows the base composition and distribution of repetitive DNA elements

Question 52

What do you see in G-banding?

Answer 52

black and white alternating pattern

Question 53

What happens in Leptotene?

Answer 53

you have separated homologues, sister chromatids are very close to each other and start to condense

Question 54

What happens in zygotene?

Answer 54

sister chromatids begin to form a complex by synapsing; they line up by their entire length

Question 55

what happens in pachytene?

Answer 55

the sister chromatids are now a tetrad and undergo crossing over

Question 56

What happens in diplotene?

Answer 56

the bivalent are together, you have a chiasma which is where crossing over occured

Question 57

What happens in diakenesis?

Answer 57

the bivalents separate

Question 58

when does spermatogenesis start occuring

Answer 58

at puberty

Question 59

Where are sperm formed?

Answer 59

in seminiferous tubules of testes

Question 60

What forms spermatogonia?

Answer 60

primordial germ cells

Question 61

In the developmental stage, what is the final cell type?

Answer 61

primary spermatocyte

Question 62

What happens with the primary spermatocyte?

Answer 62

It undergoes meiosis 1, forming 2 halpod secondary spermatocytes

Question 63

What cell type of spermatogenesis undergoes meiosis 2?

Answer 63

secondary spermatocyte to form four spermatids that later form sperm

Question 64

When does oogensis occur?

Answer 64

at prenatal development

Question 65

Into what does oogonia develop and does the resulting cell undergo meiosis 1 or 2?

Answer 65

oogonia develop into primary oocyte and then undergo meiosis 1

Question 66

What happens with the primary oocytes that do not degenerate?

Answer 66

they remain in prophase 1 until menstruation

Question 67

What happens before ovulation?

Answer 67

oocyte compeltes meiosis 1 becoming a secondary oocyte and first polar body

Question 68

When does meiosis 2 proceed in oocyte?

Answer 68

after fertilzation to produce a fertilized mature ovum and second polar body

Question 69

How long is S phase?

Answer 69

6-8 hours

Question 70

How long is G1, S, G2 phase?

Answer 70

16-24 hours

Question 71

How long is mitosis?

Answer 71

1-2 hours

Question 72

Where are the most g bands? the least?

Answer 72

prophase; metaphase

Question 73

formation of the mitotic spindle

Answer 73

prophase

Question 74

nuclear membrane breaks up

Answer 74

prometaphsae

Question 75

maximal condensation

Answer 75

metaphse