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Genetics- Katie > Chapter 11 lecture 11 > Flashcards

Chapter 11 lecture 11 Flashcards

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Biology 101 flashcards
1
Q

what are shortened telomeres associated with?

A

shorter life span
- increase incidence of disease

proof: Romanian orphans in orphanages has shorter telomeres than children who grew up with foster parents of biological parents

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2
Q

Topoisomerase

A

enzyme responsible for adding and removing turns in the coil

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3
Q

supercoiling

A

one types of DNA tertiary structure

- takes place when the DNA helix is subjected to strain by being overwound or underwound

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4
Q

Positive supercoiling

A

models of DNA that are overrotated

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5
Q

negative supercoiling

A

molecules of DNA that are underrotated

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6
Q

A DNA molecule 300 bp long has 20 complete rotation. This DNA is:

a. positively supercoiled
b. negatively supercoiled
c. relaxed

A

b. negatively supercoiled

DNA has approx. 10 bp per turn
so 100 BP would have 10 turns

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7
Q

plasmid

A

small circular DNA molecule within a bacterial cell that is physically separate from the chromosomal DNA and replicated independently
- bacteria use them to shuttle genes around

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8
Q

How does bacterial DNA differ from eukaryotic DNA?

A

Bacterial DNA is not complexed to histone proteins and is circular

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9
Q

Euchromatin

A
  • undergoes the normal process of condensation and decondensation in the cell cycle
  • looseley condensed
  • replicated throughout S phase
  • often transcribed
    common crossover
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10
Q

heterochromatin

A

remains highly condensed state throughout the cell cycle

  • at centromeres and telomeres
  • replicated late S phase
  • cross over not common
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11
Q

histones

A

small, positively charged proteins of 5 major types

  • have high % of Arg and Lys
  • package and order the DNA
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12
Q

nucleosome core

A

basic unit of DNA packaging in eukaryotes consisting of a segment of DNA wound in sequence around 8 core histone proteins
- fundamental repeating unit of chromatin

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13
Q

chromatosome

A

a histone octamer, 1 molecule of linker histone, and 166 bp of DNA
- the linker histone (H1) is a binding agent, acting like a finger holding down the DNA preventing its release

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14
Q

linker DNA

A

double-stranded DNA inbetween 2 nucleosome cores that, in association with histone H1, holds the cores together
-30-40 bp

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15
Q

Chromatin

A

DNA + protein

H1 is the LOCK

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16
Q

how long is the DNA wrapped around the nucleosome?

A

145-147 bp

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17
Q

Neutralizing their positive charges would have which effect on the histone proteins?

a. they would bind DNA tighter
b. they would separate from the DNA
c. they would no longer be attracted to each other
d. they would cause supercoiling of the DNA

A

B. they would separate from the DNA

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18
Q

What 2 things help to compartmentalize the genome into domains of different transcriptional potentials?

A

DNA Methylation
and
Histone modification

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19
Q

Methylation of DNA

A

tightens it forming heterochromatin

thus low methylation = euchromatin

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20
Q

How many copoes of H2B histon would be found in chromatin containing 50 nucleosomes?

a. 5
b. 10
c. 50
d. 100

A

d. 100

there are 2 in every nucleosome

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21
Q

polytene chromosome

A

created by repeated rounds of DNA replication with no cell division
- often in insect salivary gland cells

22
Q

Chromosomal puffs

A

regions of relaxed chromatin where active transcription is taking place
- localized swellings of the chromosome

23
Q

DNase I sensitivity

A

correlates with gene activity

  • an enzyme that digests DNA but function to digest depends on chromatin structure
  • more sensitive to unbound DNA
24
Q

Epigenetic changes

A

methylation ; capable of being reversed and often due to environmental factors

25
Q

epigenetics

A

a heritable alteration of phenotype because of altered chromatin structure (histone modification) or the modification of DNA (methylation) without changing the DNA sequence
- NO DNA SEQUENCE CHANGE

26
Q

Acetylation of DNA

A

tends to loosen the DNA

  • leads to unwinding
  • changes their ability and compliance
27
Q

centromere structure

A

region of the chromosome in which spindles attach

  • surrounded by heterochromatin, essential for chromosome separation
  • acts as site of assembly of the kinetochore
28
Q

telomere structure

A

a region of repetitive nucleotide sequences at each end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes

  • G-rich strand at the telomere is longer than the C-rich strand
  • in mammals the G-rich strand folds over and pairs with a short stretch of DNA to form a t-loop
29
Q

Human telomere sequence

A

5’- (TTAGGG)n -3’

-

30
Q

kinetochore

A

highly complex multiprotein structure that is responsible for the actual events of chromosome segregation
i.e. binding microtubules and signaling to the cell machinery

31
Q

What s a characteristic of DNA sequences at the telomeres?

a. one strand consists of guanine and adenine (or thymine) nucleotides
b. they consist of repeated sequences
c. one strand protrudes beyond the other, creating some single-stranded DNA at the end.
d. all of the above

A

d all the above

32
Q

What happens to a chromosome that loses it’s centromere?

A

It will not segregate into the nucleus in mitosis and is usually lost

33
Q

C value

A

the amount of DNA per cell

- a quantity termed in eukarotic organisms

34
Q

denaturation

A

melting point

35
Q

renaturation

A

when slowly cooled single-stranded DNA will collide and hydrogen bonds will form again between complementary base pairs to form dsDNA

36
Q

Unique sequence DNA

A

sequences that are present only once or at most a few times in the genome

37
Q

moderately repetitive DNA

A

typically consist of DNA sequences from 150-300 bp in length that are repeated many thousands of times

38
Q

tandem repeat sequeces

A

type of moderately repetitive DNA

- appear one after another and tend to be clustered at particular locations on the chromosome

39
Q

interspersed repeat sequences

A

are scattered throughout the genome
type of moderately repetitive DNA
- remnantants of transposable elements

40
Q

SINES

A

short interspersed elements
ex alu sequences
- short sequences that are remnants of retroviruses

41
Q

LINES

A

long interspersed elements

ex L1

42
Q

highly repetitive DNA

A

short sequences often

43
Q

most of the genes that encode proteins are found in?

a. unique sequence DNA
b. moderately repetitive DNA
c. highly repetitive DNA
d. all of the above

A

a. unique sequence DNA

44
Q

Microsatellite DNA

A

consists of a tract of tandemly repeated (i.e. adjacent) DNA motifs that range in length from two to five nucleotides, and are typically repeated 5-50 times.

  • ex. TATATATATATA
  • used for mapping location within the genome
  • each person has a unique “fingerprint” of microsatellites which is useful in forensics
45
Q

endosymbiotic theory

A

proposes that mitochondria and chloroplasts were once free living bacteria that became internal inhabitants of early eukaryotic cells . over time many of original gene lost because nuclear genes existed or were transferred to the nucleus

46
Q

What evidence supports the endosymbiotic theory?

A
  • many modern protists are hosts to endosymbiotic bacteria
  • mitochondria are similar in size to eubacteria and have their own DNA and ribosomes
  • antibiotics tha tinhibit protein synthesis in eubacteria also inhibit protein synthesis in mitochondria
  • gene sequences in mtDNA and cpDNA are most similat to eubacterial DNA sequences
47
Q

Uniparental inheritance

of organelle-encoded traits

A

animal mtDNA inherited almost exclusively from female parent

48
Q

replicative segregation

A

in heteroplasmic cells: organelles segregate randomly into the two progeny cells

49
Q

in a few organisms, trains encoded by mtDNA can be inherited from either parent. This observation indicated that in these organisms

a. mitochondria do not exhibit replicative segregation
b. heteroplasmy is present
c. both sperm and eggs contribute cytoplasm to the zygote
d. there are multiple copies of mtDNA in each cell

A

c. both sperm and eggs contribute cytoplasm to the zygote

50
Q

in its organization, chloroplast DNA is most similar to

a. eubacteria
b. archaea
c. nuclear DNA of plants
d. nuclear DNA of primitive eukaryotes

A

a. eubacteria

Genetics- Katie (15 decks)

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