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GENETICS PBL > CHAP 2 > Flashcards

CHAP 2 Flashcards

1
Q

What is the function of DNA polymerase?

A

travels along the single DNA strand and adds free nucleotides to 3’ end of the strand (replication always occurs 5’ to 3’

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2
Q

What is upstream and what is downstream?

A

5’ direction is upstream, 3’ direction is downstream

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3
Q

What are pyrimidines?

A

single carbon-nitrogen rings (Cytosine and thymine)

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4
Q

What are purines?

A

double carbon-nitrogen rings (adenine and guanine)

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5
Q

What makes up the sides of the double helix? and the middle?

A

sides- sugar and phosphate held together by phosphodiester bonds, chemical bonds held together by hydrogen bonding create the steps

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6
Q

What allows the replication process to occur more quickly?

A

replication origins and bubbles

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7
Q

What mediates transcription and translation?

A

RNA

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8
Q

How does RNA differ from DNA?

A

RNA contains ribose instead of deoxyribose, and uracil rather than thymine, It is also a single strand.

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9
Q

What is transcription

A

RNA is formed form a DNA template (mRNA)

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10
Q

Describe sense and antisense strands

A

When transcription begins, RNA polymerase binds to a promoter site on the DNA which seperates the DNA strands. The DNA strand that serves as a template is the antisense strand and the remaining strand is the sense strand (should be identical to the mRNA being transcribed)

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11
Q

What helps the RNA molecule from being degrade during synthesis?

A

5’ Cap- a chemically modified guanine nucleotide

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12
Q

After a termination sequence is reached what happens to the RNA strand?

A

100 - 200 adenine bases are added to the 3’ side –> poly-A tail PRIMARY TRANSCRIPT IS FORMED

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13
Q

What is the chain of interactions that increase transcription?

A

enchancer –> activator –> coativator –> general transcription complex –> gene

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14
Q

Describe the helix-turn-helix motif.

A

Two alpha-helices connected by a short chain of AA– HOX genes can cause synpolydactyly (BIND TO DNA GROOVE)

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15
Q

Describe a helix-loop-helix motif.

A

One short and one long helix connected by a flexible loop –Mutation in TWIST gene (Saethre-Chotzen syndrome)

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16
Q

Describe a zinc finger motif.

A

Zinc molecules that stabilize AA structures (BIND TO DNA GROOVE)– Breast cancer gene, Wilms tumor gene (WT1), Vit D receptors (rickets)

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17
Q

Describe a leucine zipper motif.

A

2 leucine-rich alpha-helices held together by AA side chains (BIND TO DNA GROOVE) –RB1 (retinoblastoma genes)

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18
Q

Describe a beta-sheet motif.

A

Side chains extend from 2 beta sheets to form contacts with DNA helix –TBX5 (Holt-Oram syndrom) TBX3 (ulnar mammary syndrome)

19
Q

What are euchromatins?

A

TRANSCRIPTIONALLY ACTIVE opened/decondensed chromatin regions, characterized by histone acetylation (attachment of acetyle groups to lysine residue in histones)

20
Q

What are heterochromatins?

A

Less acetylated more condensed and transcriptionally inactive chromatin regions

21
Q

Describe the change from a primary mRNA transcript to a mature mRNA transcript.

A

Introns are spliced OUT and exons are left to code for proteins. mRNA then moves into the cytoplasm

22
Q

What are the three STOP codons?

A

UAG UUA UGA

23
Q

What is translation?

A

mRNA interacts with tRNA to synthesize polypeptides

24
Q

Where does rRNA bind to and what is its function?

A

rRNA binds to the initiation site on the mRNA– methionnine (AUG). It binds tRNA and mRNA

25
Q

Osteogenesis imperfecta is a defect in what protein?

A

Collagen Type I

26
Q

Which osteogenesis imperfecta subtypes is caused by mutations in two genes?

A

I-IV

27
Q

What is amino acid is critical to proper folding of the triple helix in formation of collagen? (It is present at every 3rd position of the polypeptide)

A

Glycine **if replaced by another amino acid instability occurs bc glycine is the only AA small enough to accommadate in the center of the triple helix structures

28
Q

What is the consensus sequence?

A

DNA sequence that direct splicing enzymes to specific locations

29
Q

What are the three types of DNA that are seen in our genome

A
  1. Single-copy genes (45%) 2. Dispersed repetative DNA (45%) 3. Satellite DNA (10%)
30
Q

What percent of the genome is composed of minisatellites and microsatellite DNA?

A

3%

31
Q

Describe the Alu repeat

A

It is a SINE, wwith ALu repeats that contain DNA sequence that can be cut by the Alu restriction enzyme. They make up 10% of the genome

32
Q

What happens during G1, S, and G2 stages?

A

G1: synthesis of RNA and proteins
S: DNA replication
G2: some DNA repair takes place, cell prepares of mitosis

33
Q

Meiosis I is also called..

A

reduction division stage- 2 haploid cells from 1 diploid cell

34
Q

Meiosis II is also called..

A

equational division stage- haploid cells are duplicated

35
Q

What phase differentiates meiosis from mitosis, what specifically?

A

Prophase I, synapsis- homologous chromosomes line up side by side and formation of chiasma- crossing over of chromosomes to exchange genetic materials

36
Q

What characterizes the beginning of metaphase in both meiosis and mitosis?

A

The completion of spindle formation

37
Q

At what stage does the chiasmata disappear?

A

Anaphase I

38
Q

What marks the beginning of telophase I?

A

the chromosomes reach the opposite side of the cell

39
Q

What is the difference between interphase I and II?

A

in interphase II there is no DNA replication

40
Q

How many chromosomes are present in a spermatogonia?

A

Diplod

41
Q

At what stage does sperm become haploid?

A

After meiosis II, when they become spermatids

42
Q

What stage is oogenesis arrested at before birth?

A

Prophase I

43
Q

When does meiosis II begin in secondary oocytes?

A

Fertilization by sperm cell

44
Q

What happens at ovulation?

A

Meiosis I is completed so there is a secondary oocytes (haploid) and polar body

GENETICS PBL (3 decks)

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