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BIOL 1001 > Lecture 4 - DNA and Protein Synthesis > Flashcards

Lecture 4 - DNA and Protein Synthesis Flashcards

1
Q

what is the nucleus’ function?

A

-control centre of cell
-contains cellular DNA
-eukaryotic (not in prokaryotes)

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2
Q

how many nuclei do cells have?

A
  • most have 1
    -RBC have 0
    -muscle cells have multiple
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3
Q

what is the nuclear envelope function

A

-separates nucleus from cytosol
-protects from damage
-reacts to enviro to regulate gene expression

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4
Q

what is the function of nuclear pores

A
  • allow passage of ions and molecules but too small for proteins and DNA
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5
Q

what is DNA?

A
  • deoxyribonucleic acid
  • primary genetic material
    -central role in hereditary and genetics
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6
Q

describe the shape of DNA

A

-2 chains paired together and twines into helix shape
-tightly wound around histones
- each strand has backbone made of alternatine sugar (deoxyribose) and phosphate groups
-each sugar has A, T, G, C attaches
-bases attaches w H bonds

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7
Q

what is a histone

A

protein that provides structural support for chromosome (compacts DNA)

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8
Q

what are genes

A

segments of DNA to encode proteins (not all genes encode proteins)
- nucleotide triplets that specify sequences of AA

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9
Q

what is a chromosome?

A

DNA molecules that are tightly woven

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10
Q

how many pairs of chromosomes do we have

A

23 (1 mother, 1 father per pair)
- 22 autosomal, 1 sex- XX vs XY

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11
Q

what does a gene do?

A

each gene is a code to build a short strand of RNA (mRNA; messenger RNA)

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12
Q

what is helicase?

A

-enzyme to break H bonds, and unwind ds into ss DNA
-basically unzipping
-5’ to 3’

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13
Q

what is DNA polymerase

A

-binds to expose base on ss & draws in free nucleotides from nucleoplasm

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14
Q

what is a nucleotide

A

single segment of sugar, phosphate and base (A, T, G, C, U)

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15
Q

how does the leading strand synthesize?

A

continuously

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16
Q

how does the lagging strand synthesize?

A
  • in short discontinous fragments
    -called okazaki fragments
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17
Q

what is an okazaki fragment

A

small sections of DNA that are formed during DNA replication from laggin strand

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18
Q

how is DNA directionality determined

A

based on orientation of polarity

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19
Q

what direction do strands run in after they are separated

A

antiparallel; complimentary

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20
Q

which direction can DNA polymerase transcribe

A
  • can only transcribe in one direction continuously (5’ to 3’)
21
Q

how is the top strand (leading strand) transcribed?

A
  • all at once, towards replication fork
  • only requires one DNA pol. since it is continous fragment
22
Q

how is the bottom (lagging) strand transcribed?

A
  • in small sections, away from replication fork
    -requires multiple DNA polymerases + DNA ligases to splice segments together
23
Q

which is the parent and which is the daughter strand

A

parent: OG
daughter: newly replicated (mRNA)

23
Q

what is DNA ligase?

A

-enzyme required for repair, replication, and recombination
- catalyze formation of phosphodiester bonds at ssDNA

24
Q

what is the end result of DNA replication

A
  • 2 DNA molecules from OG
    -identical to OG
    -each one has 1 old and 1 new strand
    -coding base pairs lost with each replication
25
Q

how do you prevent loss of coding material?

A
  • telomeres on each DNA molecule
26
Q

what is a telomere

A
  • protective non-coding end
    -prevents damage during mitosis
  • think aglet
27
Q

what happens when telomeres become too short

A

chromosome can no longer replicate

28
Q

what type of replication occurs?

A

semiconservative replication!

29
Q

what is RNA?

A

-ribose nucleic acid
-created using coding from DNA
-A, C, G, U (A-U, C-G)

30
Q

what is mRNA?

A

-messenger RNA
-codes for protein synthesis
-able to leave nucelus and enter cytoplasm

31
Q

what are the steps of protein synthesis?

A

transcription and translation

32
Q

what are the basics of transcription?

A
  • RNA polymerase unwinds DNA (template) and starts RNA formation (coding strand)
    -transcribed in triplets (codons)
33
Q

why is mRNA needed?

A
  • DNA too big to leave cell, instead makes copy via mRNA which is able to leave via nuclear pores
34
Q

what happens to mRNA before it leaves the nucleus?

A

-edited via:
- introns removed (non coding triplets)
-exons remain (coding triplets)
-5’ cap (guanine) and 3’ poly A tail (adenine) added

35
Q

why are caps and tails added?

A
  • to protect strand
    -initiate/stop protein synthesis
36
Q

what are the basics of translation?

A

-mRNA leaves N –> cytoplasm
-attaches to ribosome
-each codon reads for complimentary anti-codon attached via tRNA
- 1 anti codon = 1 tRNA = 1 AA
- AA connected via peptide bonds to form polypeptide chains & proteins

37
Q

what are the start codon

A

AUG

38
Q

what are the stop codons

A

UAA, UAG, UGA

39
Q

what happens when strand is finished being coded?

A

-detaches from ribosome and:
- remains in cytoplasm,
-transferred through ER to GA and transported out of cell via vesicles via exocytosis

40
Q

what are constitutively active genes?

A
  • continuously being transcribed regardless of outside stimuli
41
Q

what are regulated genes?

A

genes that can be induced or repressed as needed

42
Q

what is a base substitution mutation?

A

wrong base in wrong place (A instead of G)

43
Q

what is a deletion mutation?

A

missing base (ATGC –> AT_C)

44
Q

what is an insertion mutation?

A

new bases that weren’t there before

45
Q

what is a silent mutation?

A
  • when base subsitition occurs but the codon ends up encoding for the same AA; thus no change to function
    -usually happens when third position of codon changes
46
Q

what is a missence mutation?

A
  • when base sub results in different AA
    -conservative; similar function, little affect
    -noncons.; very different, lead to poor outcome (sickle cell anemia)
47
Q

what is a nonsense mutation?

A

-when base sub results in stop codon which stops translation early leading to non functional protein

48
Q

what causes mutations?

A

-errors in DNA replication
-chemical damage (meds, exposure, enviro, chemo)
-radiation (uv, xrays, cancer treatment)

BIOL 1001 (15 decks)

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