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Bio 1 (101-NYA-05) > Lecture 8-9: Genes, Gene Expression and Mutations > Flashcards

Lecture 8-9: Genes, Gene Expression and Mutations Flashcards

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1
Q

chromatin

A

DNA in eukaryotic cells is bound to special proteins that act as spools, condensing and protecting the DNA molecule

DNA + Protein = chromatin

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2
Q

what are the proteins associated with DNA (for chromatin) called?

A

histones

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3
Q

when i chromatin seen

A

when the cell is not dividing

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4
Q

name the types of chromatin in eukaryotic cells

A
  • euchromatin

- heterochromatin

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5
Q

euchromatin

A

not easily visible, loose chromatin that is found throughout the nucleus

  • loose lightly packed chromatin
  • rich in genes
  • comprises the most active portion of the genome of any given cell (gene expression)
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6
Q

heterochromatin

A
  • tightly packed DNA when the cell is not dividing

- represents the inactive portion of the genome. genes are silenced (no gene expression)

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7
Q

chromosomes (when formed… of what)

A

when a cell is ready to divide, the chromatin is tightly packaged nd condensed to form chromosomes

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8
Q

how many pairs of chromosomes do humans have

A

23 pairs

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9
Q

genes

A

discrete unit of the hereditary information consisting of a specific nucleotide sequence in DNA

always located on a specific location (gene locus)

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10
Q

gene locus

A

specififc location where genes are always located

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11
Q

how does DNA lead to specific traits

A

by dictating the synthesis of proteins

every gene is like a recipe for a single product, a single polypeptide

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12
Q

genome

A

the genetic material of an organism or virus; the complete complement of an organism’s genes along with its noncoding nucleic acid sequences

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13
Q

is number of genes related to genome size

A

no

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14
Q

who has lowest gene density. why?

A

humans and other mammals due to large amount of non-coding DNA between genes

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15
Q

telomeres

A
  • when eukaryotic ells divide, the chromosomes get shorter bc the ends are not fully replicates
  • to protect genes of eukaryotic cells from being eroded, non-coding DNA sequences at their ends are called telomeres
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16
Q

telomeres are a repetition of which nucleotide sequence. repeated how many times

A

TTAGGG

100-1000 times

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17
Q

telomerase

A

germ cells have an enzyme called telomerase that catalyzes the lengthening of telomeres in eukaryotic germ cells

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18
Q

gene expression

what are the stages?

A

process by which DNA directs the synthesis of proteins

  1. transcription
  2. translation
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19
Q

triplet code

A

genetic instructions for a polypeptide chain are coded as a series of non-overlapping, three nucleotide

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20
Q

transcription

A

DNA -> RNA

genetic information in the form of DNA is used as a template to generate a molecule of RNA

21
Q

stages of transcription

A
  1. initiation
  2. elongation
  3. termination
22
Q

RNA polymerase function

A
  1. binds to a specific gene region on the chromosome
  2. separates double helix at a specific gene region
  3. DNA read form 3’-5’ and transcribed into messenger rna
  4. transcription occurs 5’-3’
  5. mrna strand is complementary to DNA
23
Q

transcriotion - initiation

A

RNA polymerase binds to teh DNA molecule and splits the double helix

24
Q

transcription - elongation

A

RNA polymerase reads the 3’-5’ DNA strand

RNA polymerase synthesizes a mRNA strand from 5’-3’

the mRNA strand is the compliment to the DNA template (strand it reads)

25
Q

transcription termination

A

RNA polymerase reaches the end of the gene and detaches

DNA double helix reforms
mRNA leaved the nulceus

26
Q

template strand

A

the strand of DNA that is transcribed

27
Q

coding strand

A

the strand of DNA that is NOT transcribed

28
Q

are the template and coding strands complementary?

A

yes

29
Q

Translation

A

RNA -> proteins

30
Q

codons

A

triplet code found on mRNA

31
Q

tRNA

A

each tRNA molecule has a 3D conformation due to stretches of complimentary bases

  • contain anticodon: nucleotide triplet which base pairs with a complimentary codon of the mRNA
  • at the other end of the tRNA molecule is a bonding site for a specific amino acid
32
Q

ribosomes - translation

A

made of 2 subunits: large and small subunit composed of proteins and rRNA molecules

  • where the synthesis of polypeptide occurs
  • facilitate the specific coupling of tRNA anticodons with mRNA codons by holding tRNA and mRNA close together, enabling the addition of amino acids to the growing polypeptide chain
33
Q

translation initiation full steps

A
  1. small ribosomal subunit binds to mRNA
    it scans the mRNA for the start codon (AUG) and binds to the mRNA at that location
  2. the initiator tRNA binds to the mRNA at start codon
    the initiator tRNA carries the anti-codon UAC which is complementary to the start codon (AUG)
  3. large ribosomal subunit binds
    the binding of the large subunit requires energy
34
Q

translation steps (names)

A
  1. codon recognition
  2. peptide bond formation
  3. translocation
35
Q

translation - codon recognition

A

the anticodon of an incoming aminoacyl tRNA base pairs with the complimentary tRNA base pairs with the complementary mRNA codon A site

36
Q

translation - peptide bond formation

A

a peptide bonds is formed between the new amino acid at the A site and the growing polypeptide at the P site; this step attaches the polypeptide to the tRNA at the A site

37
Q

translation – translocation

A

ribosome translocates the tRNA in the A site to the P site

the mRNA is moved through the ribosome (it is not the ribosome that is moving along the mRNA) 5’ end first

empty tRNA in the P site is moved to the E site, where it is released; the mRNA moves along with its bouns tRNA’s, bringing the next codon to be translated into the A site

38
Q

translation termination

A

elongation occurs until the stop codon arrives at the A site

a protein called a release factor binds to the A site

39
Q

what are mutations

A

changes in the nucleotide sequence of an organism’s DNA

they are responsible for the huge diversity of genes fund among organisms because mutation are the ultimate source of new genes

40
Q

small scale mutations

A

point mutations: changes in a single nucleotide pair of a gene

  • if it occurs in a gamete or cell that gives rise to gametes, it may be transmitted to offspring
  • if the mutation has an adverse effect on the phenotype of an organism, the mutant condition may be referred to as a genetic disorder or hereditary disease
41
Q

base pair substituions (nucleotide-pair substitution, silent mutations)

A
  • nucleotide-pair substitution: replacement of one nucleotide and its partner with another pair of nucleotides
  • silent mutations: base-pair substitution that has no effect on the coded protein owing to the redundancy of the genetic code
42
Q

missense mutations

A

base pair substitutions that change one amino acid to another

such a mutation may have little effect on the protein:

  • new amino acid may have similar properties as the one it replaces
  • new amino acid may be in a region of the protein where the exact sequence of amino acids is not essential to function
43
Q

nonsense mutations

A
  • base pair substitutions that change one amino acid into a stop codon
  • causes translation to be terminated prematurely
    resulting polypeptide will be shorter
  • nearly all nonsense mutations lead to nonfunctional proteins
44
Q

insertion and deletions

A

additions or losses of nucleotide pairs in a gene

  • causes translation to be terminated prematurely: have disastrous effect on the resulting protein more often than substitutions do
45
Q

frameshift mutation

A

when an insertion or deletion alters the reading frame of the genetic message, the triplet grouping of nucleotides on mRNA that is read during translation

46
Q

what mutation

ACU to ACC

(thr to thr)

A

silent

47
Q

what mutation

CAU to CAA
len to gln

A

missense

48
Q

what mutation

UGC to UGA
UGA = stop

A

nonsense

Bio 1 (101-NYA-05) (8 decks)

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