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Unit 4: Genetics Flashcards

1
Q

In DNA replication Topoisomerase..

A

…helps relieve this strain by breaking,and rejoining DNA strands

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2
Q

DNA replication is considered semiconservative because…

A

Each half of the original parent strand serves at the template for the new complementry strand.

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3
Q

In DNA replication Helicase…

A

Breaks the Hydrogen bonds that holds the strand together and begins to unwind the molecule.

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4
Q

In DNA replication SSBs (single strand bonding proteins)…

A

Binds to each single DNA strand and prevents the strand from reforming its Hydrogen bonds.

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5
Q

In which direction does DNA replication occur

A

5’ to 3’ direction

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6
Q

Leading Strand vs. Lagging Strand

A

works toward replication fork / works away from replication fork.

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7
Q

In DNA replication DNA Primase…

A

Lays down short RNA primers so that DNA polymerase 3 recognizes where to attach to the strand and begin building the new complementary DNA strand.

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8
Q

In DNA replication DNA polymerase III…

A

Adds the correct nucleotide triphosphates to the 3’ end of the new strand using the template as a guide. (Phosphate bond).

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9
Q

In DNA replication Okazaki fragments…

A

Grows discontinuously, in short segments, away from the replication fork.

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10
Q

in DNA replication DNA Polymerase 1…

A

Removes RNA primers and correcting incorrect nucleotides.

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11
Q

In DNA replication DNA Polymerase 2 and 1 …

A

Repairs damage to DNA including periods of damage during replication it also proof reads the newly formed strands.

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12
Q

In DNA replication DNA Ligase…

A

Joins the gaps between corrected Okazaki fragments of DNA by creating phosphodiester bonds.

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13
Q

In what phase does cell division occur?

A

Interphanse, the S Phase

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14
Q

Why did scientists need to refine the one gene-one protein hypothesis?

A

Some genes code for many protein

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15
Q

What does RNA polymerase participate in?

A

DNA transcription

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16
Q

In a DNA nucleotide, the number 3 carbon of the deoxyribose sugar bonds with?

A

A phosphate of another nucleotide

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17
Q

What is the Central Dogma

A

The flow of genetic information from DNA to RNA to proteins

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18
Q

When comparing the structure of DNA in eukaryote and prokaryotes, what is true?

A

Eukaryotes contain DNA in homologous chromosome pairs and in mitochondrion and chloroplasts.

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19
Q

Which statement about telomeres are true?

a) they can provide starting points for replication
b) they prevent the loss of genes from the ends of chromosomes during replication.
c) they are located at the ends of chromosomes.
d) all of the above

A

d) all of the above

20
Q

Heterochromatin

A

Condensed portions of chromatins. In this closed configuration, genes can not have their code copied into polypeptide chains. Some portions of chromatin are permanently condensed and their genes are never expressed. During cell division, all chromatin exists as heterochromatin.

21
Q

Euchromatin

A

When genes are active , the chromatin isn’t tightly coiled or condensed, but is in an open configuration.

22
Q

What are the two stages of Protein Synthesis in order?

A
  1. Transcription 2. Translation
23
Q

what occurs in the first step of Transcription?

A
  1. initiation - DNA is unwound and unzipped (Helicase) in area of the gene that is to be transcribed by RNA polymerase which binds to the promoter region ‘upstream’ of gene.
24
Q

What is the promoter region?

A

signals which DNA strand is to be copied. this region is ‘upstream’ of the gene that needs to be copied and has high concentration of the T’s and A’s in eukaryotes.

25
what are the post Transcriptional mRNA modifications?
in Eukaryotes this occurs before leaving the nucleus 1. capping - a 5' cap of 7 Guanines is added to the start of the pre-mRNA. (functions as the initial attachment site for mRNA to ribosomes.) 2. Tailing - 50 to 250 adenine are added nucleotides are added to the 3' end = poly A tail 3. Introns ( non coding region) - are removed before translation by spliceosomes so that only exons (coding regions) remain. modified strand now called mRNA transcript
26
What occurs in the first step of Translation?
1. Initiation - starts when a methionine-tRNA (p site) forms a initiation complex with the Small Ribosomal subunit. This complex binds to the mRNA Transcript (at the 5' cap) and scans the mRNA Transcript until it reaches the AUG codon (start codon). The Large Ribosomal subunit then binds to complete the Ribosome. Initiation complex is not fully formed and .the correct reading fram is established in the P site. (middle)
27
what is tRNA?
is a single stranded nucleic acid. it contains an anticodon (sequence of 3 bases) that recognizes the codon (sequence of 3 bases) on the mRNA transcript. each tRNA carries a corresponding amino acid.
28
what occurs in the second step of Translation?
2. Elongation - After the initiation complex is formed the second tRNA with the correct anticodon and amino acids binds to the mRNA codon in the A site. The amino acid carried by the met tRNA is cleaved by peptidyl transferase in the P site and a peptide bond it formed between it and the amino acid of the tRNA in the A site. the now empty met-tRNA moves into the E site the second tRNA moves into the P site and the A site is empty. tRNA's with corresponding anticodons and amino acids move to each site until leaving through the E site. once they are empty.
29
How many codons does a mRNA strand read at a time and starting from which direction?
1 codon at a time (which is a sequence of 3 nitrogenous bases) is read on the mRNA strand in the 5' to 3' direction.
30
what are the three sites in Ribosomes the tRNA can attach to?
A (aminoacyl) site and P (peptidyl) site, and the E (exit) site.
31
In which direction does the initiation complex move.
moves along the mRNA strand in the 5' to 3' direction to the next codon.
32
What occurs in the third step of Translations?
3. Termination - there are three stop codons UGA, UAG, UAA that do not have complementary tRNA. When the stop codon enters the A site, translation ends and a protein release factor binds to the site causing the release of the polypeptide chain from the ribosome. the two ribosomal subunits seperate and detach from the mRNA. The amino acid chain is folded and modified as necessary.
33
What are mutations?
Mutations are permanent changes to a cells DNA sequence. These changes can be in the nucleotide sequence, an alteration of gene position, gene loss, duplication, or insertion of foreign substances.
34
What occurs in the second step of Transcription?
2.Elongation - with 1 DNA strand serving as the 'template strand' RNA polymerase attaches (through complementary base parings) ribonucleotides in 5' to 3' direction.
35
What occurs in the third strep of Transcription
3. Termination - RNA polymerase transcibes the DNA sequence up to the end of the gene where a 'terminator sequence' is encountered. Then the pre-mRNA transcript is released from the DNA strand
36
What is a Mutagens?
Any agent that causes changes in DNA. this includes physical agents that damage DNA such as x-rays, UV rays etc.
37
What are small scale mutations?
small scale mutations include point mutations that are caused by the change of a single base pair and those caused by changes to a small group of base pairs. (4 group functional small scale mutations)
38
what are large scale mutations?
These mutations can involve multiple nucleotides, whole genes, or whole sections of chromosomes. These kinds of chages to the DNA of an organism can cause a wide variety of effects. Amplification or gene duplication results in more copies of a gene or a group of genes.
39
Silent Mutation
change in nucleotide sequence that doesn't alter amino acid in a polypeptide chain. (small scale)
40
Missense Mutation
Change in one codon that alters one amino acid in a polypeptide chain. (small scale)
41
Nonsense Mutation
an amino acid changed to a stop codon. Produces a non-functional polypeptide. (small scale)
42
Frame-Shift Mutation
deletions or insertions of nucleotides changing the reading frame of the gene. (small scale)
43
Translocation Mutation
relocation of groups of base pairs from one chromosome to another. This usually occurs between two non-homologous chromosomes. New proteins can result. Substitution can be a type of translocation. (large scale)
44
Inversion Mutation
a sequence of DNA is inverted (reversed). Can disrupt base pairings. (large scale)
45
Deletion
involves loss of genetic material. (large scale)
46
Duplication
involves the copying of a DNA sequence so that there are 2 copies on one chromosome.

Biology (2 decks)

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