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Exam 1 > MGD 6-7 > Flashcards

MGD 6-7 Flashcards

1
Q

what is the sequence of molecules to forming genes?

A

base (GATC)

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2
Q

how does DNA package?

A

DNA wrapped around histone core of nucleosome
in between are linker DNA of nucleosome
beads on string ^ (genes expressed)
OR solenoid - coiled up tightly - genes not expressed

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3
Q

what are genes and where are they?

A

genes carry code for proteins and have a chromosomal location

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4
Q

what is the human genome?

A

the entire DNA sequence of human genome (24 chromosomes - 22 + 2 sex chromosomes X & Y)

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5
Q

what is the structure of DNA? what are polynucleotides?

A

DNA and RNA are nucleic acids

polynucleotides = linear polymers of nucleotides

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6
Q

what are nucleosides and nucleotides

A

nucleosides: base + sugar
nucleotide: base + sugar + phosphate (-ve charge)

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7
Q

RNA VS DNA

A

DNA (deoxy) without oxygen on C2 of pentose sugar

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8
Q

what are the 2 types of nitrogenous bases?

A

purine: 2 ring (A & G)
pyrimidine: 1 ring (C & T & U)

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9
Q

how do polynucleotides form?

A

DNA and RNA are polymers
nucleotides are joined via phosphodiester bonds
chain has polarity 5’ to 3’
chain has distinct ends: 5’P and 3’OH

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10
Q

how many bonds does G-C pairing have and A-T/U?

A

G-C 3 hydrogen bonds

A-U 2 hydrogen bonds

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11
Q

what happens in order for nucleic acids to form duplex structure (helix)

A 
bind in antiparallel
1 chain 5' --> 3'
another chain 3' --> 5'
strands have to be complementary
DNA-DNA, DNA-RNA, RNA-RNA
DNA helix is antiparallel
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12
Q

how do RNA stem loops form?

A

hydrogen bonds are formed between antiparallel, complementary sequences
e.g. tRNA (secondary structures)

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13
Q

how do you read antiparallel, complementary strands of polynucleotides?

A

top strand: 5’ –> 3’
bottom strand: 3’ –> 5’
left to right

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14
Q

describe the different stages of cell cycle

A 
G1: cell content replication
R checkpoint
S: DNA replication
G2: double check and repair any incorrect DNA sequence
cell cycle checkpoint
M: mitosis (cell division)
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15
Q

what is DNA replication catalysed by?

A

DNA polymerase

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16
Q

what are the main points in DNA replication?

A

separation of DNA strands
stepwise reaction
reaction driven by pyrophosphate hydrolysis
chain growth is directional 5’ –> 3’

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17
Q

what are the 3 main steps in DNA replication?

A

initiation, elongation, termination

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18
Q

what happens in initiation?

A

DNA helicase unzips DNA double strand
recognition of origin of replication
requires DNA polymerase
‘kick-start’ by primase attaching to the origin of replciation

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19
Q

what happens in elongation?

A

bases are attached to the 2 DNA template strands
the bottom strand (3’ –> 5’) produces the leading strand (5’–>3’)
the top strand (5’–>3’) produces lagging strand in okazaki fragments (5’–>3’) which is joined by DNA ligase
because DNA polymerase only extends (adds bases) at 3’ end

20
Q

what happens in termination?

A

when DNA ligase anneals the different sections of lagging strand
when 2 facing replication forks meet and DNA ligase joins final fragments
chromosome number stay the same
1 replicated chromosome consist of 2 (sister) chromatids

21
Q

what is the structure of chromosome?

A

classical x-shape containing 2 identical DNA molecules

sister chromatids

22
Q

when does mitosis occur?

A

cell division for somatic cells
production of 2 identical daughter cells
necessary for some tissue (epidermis, BM, spermatogonia, mucosae)

23
Q

what are the different phases in mitosis?

A

interphase, prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis

24
Q

which stages are interphase?

A

G1, R check point, S, G2, G2 check point

25
Q

what happens in prophase?

A

chromosome decondenses (out of solenoid (heterochromatin) into beads on string - euchromatin), nuclear envelope breaks down, spindle fibres form

26
Q

what happens in prometaphase?

A

spindle fibres attach to kinetochore of centromere

27
Q

what happens in metaphase?

A

chromosomes align in the equator of the cell (at metaphase plate)

28
Q

What happens in anaphase?

A

sister chromatids (daughter chromosomes) are pulled to opposite ends of the cell via kinetochore (centromere divides)

29
Q

What happens in telophase?

A

spindle fibres disintegrate
nuclear envelop reforms
chromosomes decondense

30
Q

what happens in cytokinesis?

A

cytoplasm divides

parent cell becomes 2 daughter cells with identical genetic information

31
Q

what is meiosis?

A

special cell division for germ line cells
production of 4 non-identical cells (1/2 chromosome)
1 round of replication followed by 2 rounds of division
diploid (2n) reduced to haploid (n)
production of eggs and sperm

32
Q

what are the steps in meiosis?

A

prophase I, genetic recombination through crossing over, metaphase I, anaphase I, telophase I, prophase II, metaphase II, anaphase II, telophase II + cytokinesis

33
Q

what is prophase I?

A 
line up with homologous pair (1 from mum, 1 dad)
independent assortment (4n) in equator (random assortment)
34
Q

what happens between prophase I and metaphase I?

A

genetic recombination: crossing over

35
Q

what is metaphase I?

A

spindle attach to kinetochores, homologous pairs line up in the equator of the cell

36
Q

What is anaphase I?

A

homologous pairs of chromosome pulled to opposite poles

37
Q

what happens in telophase I?

A

spindle disappears, nuclear membrane reforms, starts to split into 2 cells (2n) cytokinesis

38
Q

what happens in prophase II?

A

2 daughter cells: spindles attach to kinetochores

39
Q

what happens in metaphase II?

A

chromosomes line up in equator of cell

40
Q

what happens in anaphase II?

A

chromatids (sister) pulled to opposite poles

41
Q

What happens in telophase II + cytokinesis?

A

cells split, 23 chromatids each (1/2 single chromosome) n 4 x cells

42
Q

What are the consequences of meiosis?

A
  1. maintaining constant chromosome number of from generation to generation (23 Pairs)
  2. generation of genetic diversity
    random assortment of chromosomes
    crossing over of genetic material
43
Q

what is spermatogenesis and what does it produce and how long does it take?

A

cell division to produce male gametes
1 spermatocyte (2n) –> 4 sperm (n)
takes 48 days

44
Q

what is oogenesis, what does it produce and how long does it last for?

A

cell division to produce female gametes
1 oocyte (2n) –> 1 egg (n) + 3 polar bodies
lasts 12-50 years

45
Q

what are the consequences of faulty meiosis?

A

1/3 of all identified miscarriages
infertility
leading cause of mental retardation

Exam 1 (39 decks)

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