Chapter 2- gene structure and organization

Question 1

functions of non-coding DNA

Answer 1

• control how our genes work (transcription and translation)
• promoters and enhancers
• make non-coding RNA

Question 2

miRNA

Answer 2

• fn: silence genes by binding to mRNA and degrade it, can prevent attachment of ribosomes
• miRNA gene can be present anywhere

Question 3

how does miRNA become mature?

Answer 3

• cleaved to shorter precursor miRNA
• forms stem loop structure
• exportin exports miRNA to cyptoplasm
• further cleaved by dicer
• forms mature miRNA with help of Ago

Question 4

long ncRNAs

Answer 4

• 200 to thousands of nucleotides long

- fn: regulate allelic expression (x chromosome inactivation, imprinting), development, found in some disease states

Question 5

allele

Answer 5

any possible form in which a gene for a trait can exist, usually two alleles are inherited, one from each parent

Question 6

tiny ncRNA

Answer 6

• miRNA and siRNA is a type of tiny ncRNA

- expressed in defined cell type or at specific stage of early development

Question 7

competing endogenous RNAs

Answer 7

• “inhibitor of inhibitors”
• bind to miRNA and destroy it
• formed from pseudogenes

Question 8

what are pseudogenes?

Answer 8

• “retired” genes

- during evolution they once formed a protein, now so old they lost their capacity to code for proteins

Question 9

Repetitive DNA sequence

Answer 9

• forms significant portion of DNA
• either functional or uncertain function
• RS with uncertain function form minisatellites and microsatellites used in forensic science (DNA fingerprinting)

Question 10

transposons

Answer 10

• jumping genes
• can cut itself, wander, and join in another place
• some replicate and leave a copy in original place

Question 11

retroposons

Answer 11

• transposons with RNA intermediate
• RNA reverse transcribed into DNA
• play big rile in evolution and multiple copies of genes
• most transposons are not functional except for a few retroposons

Question 12

heterochromatin

Answer 12

• inactive form of DNA

- so condensed it cannot be transcribed

Question 13

euchromatin

Answer 13

• active part of DNA
• more relaxed/ less condensed
• has the majority of highly repetitive noncoding DNA

Question 14

advantage of DNA sequence duplication

Answer 14

• having excess protein helps to ensure that more gene product can be made
• allows for new proteins to have specialized function
• helps in evolution of gene variance (i.e. through alternate splicing)

Question 15

disadvantage of DNA sequence duplication

Answer 15

repeated DNA sequences can be prone to instability

Question 16

ortholog genes

Answer 16

genes which perform same function in different species

Question 17

paralog genes

Answer 17

genes which perform new function in different species

Question 18

endosymbiont theory

Answer 18

mitochondrial genome started as prokaryote that was engulfed by eukaryotic cell

Question 19

mitochondrial genome

Answer 19

• has own synthesizing material
• 95% of genes are functional
• all mitochondria you have as an adult comes from your mother

Question 20

chromosome

Answer 20

threadlike structure of nucleic acid and proteins found in nucleus of cell, has genetic info that forms gene

Question 21

why is genetic info tightly packed?

Answer 21

• so that DNA doesn’t get twisted in the cell

- helps to separate info properly during mitosis

Question 22

chromatin

Answer 22

genetic material that condenses to form chromosomes

Question 23

chromatid

Answer 23

makes up one section of the chromosome- half the “x” of a chromosome

Question 24

replication origin

Answer 24

sequence of DNA where protein factors bind to start replication

Question 25

centromere

Answer 25

part of chromosome that links sister chromatids

Question 26

telomere

Answer 26

end of the chromosome, helps to maintain chromosomes integrity

Question 27

what is the role of the telomore?

Answer 27

• maintain chromosomal integrity
• during replication, end of chromosome isnt replicated well so gradually lose the info there
• telomere is made up of repeated, unwanted info that is ok to lose
• when telomere is gone replication ends

Question 28

haploid cells

Answer 28

one set of chromosomes- sperm and egg cells

Question 29

diploid cells

Answer 29

two copies of chromosomes, one set from mother and one from father

Question 30

homologs

Answer 30

maternal and paternal copes of same chromosomes

Question 31

cell cycle phases

Answer 31

1. G1
2. G1-S
3. S
4. G2
5. M

Question 32

G1 phase

Answer 32

Activate genes transcribed, duplicate cell contents except for nuclear material

Question 33

G1-S phase

Answer 33

response to a signal i.e. growth factor

Question 34

S phase

Answer 34

synthesis of DNA

Question 35

G2 phase

Answer 35

check for DNA errors

Question 36

M phase

Answer 36

nuclear division (mitosis) and cell division (cytokinesis)

Question 37

What is the purpose of mitosis?

Answer 37

divide nuclear material, result is diploid cells

Question 38

what are the phases of mitosis?

Answer 38

1. prophase
2. prometaphase
3. metaphase
4. anaphase
5. telophase
6. cytokinesis

Question 39

prophase

Answer 39

• “prep” phase
• chromosome condenses
• nuclear membrane breaks down, centrosome divides
• spindles formed

Question 40

prometaphase

Answer 40

• sister chromatids become attached to spindle

- polar microtubules overlap near equator

Question 41

metaphase

Answer 41

chromosomes line up at equator

Question 42

anaphase

Answer 42

• centromere divides and each chromatid is now separate chromosome
• microtubles shorten and chromosomes move towards poles

Question 43

telophase

Answer 43

• chromosome decondenses
• spindles break down
• 2 nuclear membranes form at each pole
• shortest phase

Question 44

cytokinesis

Answer 44

distribute cytoplasm and its organelles to two daughter cells

Question 45

what is meiosis?

Answer 45

division of reproductive cells, undergoes 2 divisions

- the second division is like mitosis

Question 46

what is the result of meiosis in males?

Answer 46

four haploid sperm cells

Question 47

what is the result of meiosis in females?

Answer 47

one haploid egg and three polar bodies

Question 48

what is synapsis?

Answer 48

• joining of two pairs of sister chromatids and chromosomal material is exchanged/crossed over
• occurs during meiosis

Question 49

prophase I

Answer 49

• meiosis
• homologous chromosomes pair together, form bivalent
• process of pairing= synapsis

Question 50

metaphase I

Answer 50

• meiosis

- chromosomes move to equator

Question 51

anaphase I

Answer 51

• meiosis

- homologous chromosomes pulled to opposite poles

Question 52

how does meiosis ensure genetic diversity?

Answer 52

• recombination

- independent assortment

Question 53

what is recombination?

Answer 53

• synapsis of paternal and maternal homologs
• after replication homologs align resulting in bivalent
• DNA physically breaks from one chromosome, switches to the other
• commonly occurs in subtelometric region
• occurs during meiosis I

Question 54

what is independent assortment?

Answer 54

• alleles for one trait segregate independently from alleles for another trait
• occurs during metaphase I

Question 55

leukemia

Answer 55

• miRNA overexpressed
• moves balance to cell proliferation- results in low cell differentiation
• too many blast cells/ immature cells

Question 56

hemophilia

Answer 56

• transposons lead to unstable DNA
• due to mutation in factor VIII gene
• results in clotting deficiency