8 - Genetics

Question 1

Describe the bacteria chromosome:

Answer 1

1. single circular chromosome
2. singular DNA molecule
3. attached to plasma membrane
4. has coding and noncoding regions

Question 2

DNA replication

Answer 2

genetic information can be transferred between generations of cells (aka DNA synthesis)

Question 3

Leading strand

Answer 3

is the new strand synthesized by DNA polymerase (going towards replication fork)

Question 4

Lagging strand

Answer 4

DNA polymerase starting at replication fork and is synthesized discontinuously and made in Okazaki fragments

Question 5

Topoisomerase

Answer 5

relieves supercoiling

Question 6

Gyrase

Answer 6

relieves supercoiling

Question 7

Helicase

Answer 7

separates two strands from each other

Question 8

DNA polymerase

Answer 8

zips down toward the replication fork - only makes DNA strand 5’-3’ also can proofread

Question 9

DNA ligase

Answer 9

connects fragments to make a complete strand on the lagging strand

Question 10

DNA Replication Steps

Answer 10

1. supercoiling relieved by topoisomerase (gyrase)
2. double helix unwound by helicase
3. new nucleotides are added to two separated strands - DNA polymerase adds to 3’ end of new strand so the new strand is made 5’ - 3’ and parent strand copied 3’ - 5’
4. Parental strand is unwound further to continue replication at the replication fork

Question 11

What is DNA transcription?

Answer 11

process of copying DNA into into RNA - DNA is transcribed into RNA by RNA polymerase

Question 12

What are the 3 steps of transcription?

Answer 12

1. Initiation: RNA polymerase binds to specific regions (promoters) of DNA to start transcription
2. Elongation: RNA polymerase moves down the DNA template (3’-5’) synthesizing the RNA (5’-3’)
3. Termination: RNA polymerase reaches a DNA sequence that serves as a terminator sequence

Question 13

What is DNA translation?

Answer 13

RNA is used to make proteins - RNA is translated to proteins, in ribosomes

Question 14

Codon

Answer 14

every 3 bases

Question 15

Reading frame

Answer 15

sequence of code

Question 16

How many total codes and how many total amino acids?

Answer 16

total codes = 64
total amino acids = 20

Question 17

What are the four properties of the genetic code?

Answer 17

1. redundant (a.a. are coded by more than one codon)
2. unambiguous (single codon never codes for more than one a.a.)
3. Universal (codons specify the same a.a. in all organisms)
4. Conservative: codons that specify the same amino acid have the same first 2 bases)

Question 18

Transfer RNA (tRNA)

Answer 18

recognizes the codon and transports the corresponding amino acid and binds with anticodon

Question 19

What are the 3 sites of the ribosome?

Answer 19

1. E: tRNA with no amino acid, about to leave = “exit”
2. P: holds growing peptide chain = “peptide”
3. A: tRNA enter with an amino acid attached = “acceptor”

Question 20

Central dogma

Answer 20

DNA -> RNA -> protein

Question 21

What are some differences in transcription and translation between prokaryotes and eukaryotes?

Answer 21

1. location of transcription (p- cytoplasm; e- nucleus)
2. prokaryotes can transcribe and translate at the same time since prokaryotic cells RNA doesn’t have to leave membrane-bound organelles
3. eukaryotes have introns and exons - splicing

Question 22

What is gene regulation?

Answer 22

not all genes are needed all the time - cells conserve energy by only producing proteins they need

Question 23

What is a constitutive gene?

Answer 23

always expressed (i.e. glycolysis)

Question 24

What are operons?

Answer 24

specific for bacteria - set of genes that have a similar function that are controlled together - will make all or will make none

Question 25

What are the 3 parts of an operon?

Answer 25

1. promoter: where RNA polymerase initiates transcription 2. operator: acts as stop or go signal for transcription 3. operon genes: set of genes with similar function or goal that are controlled together

Question 26

Repressible operon

Answer 26

always on unless turned off (tryptophan synthesis genes)

Question 27

Inducible operon

Answer 27

always off unless turned on (inducible operon-Lac operon)

Question 28

What are mutations?

Answer 28

permanent change in an organism's DNA

Question 29

How are mutations caused?

Answer 29

1. spontaneously - mistakes during replication 2. mutagens - chemicals/radiation

Question 30

Missense mutation

Answer 30

point mutation changes amino acid sequence

Question 31

Silent mutation

Answer 31

point mutation does not change amino acid sequence (3rd base)

Question 32

Nonsense mutation

Answer 32

base substitution results in a nonsense codon

Question 33

Frameshift mutation

Answer 33

nucleotides are deleted or added, changing the codons

Question 34

What are the general purpose of different mutant tests?

Answer 34

identifying mutants and the mutation rate (probability a gene with mutate)

Question 35

Positive selection test

Answer 35

detects mutants by rejecting non-mutants

Question 36

Negative selection test

Answer 36

selects cells that cannot perform a function

Question 37

Ames test

Answer 37

tests a chemical/potential mutagen to determine if it cause mutations

Question 38

Recombination

Answer 38

exchange of genes b/w 2 DNA molecules; gives new gene combos

Question 39

Transformation

Answer 39

genes are transferred as "naked" DNA - bacteria release DNA into the environment other bacteria pick it up and insert into chromosome - only competent cells are able to pick it up

Question 40

Conjugation

Answer 40

transfer of a plasmid through a sex pilus - requires cell-cell contract

Question 41

Transduction

Answer 41

DNA is transferred inside a bacteria (bacteriophage)

Question 42

Bacteriophage

Answer 42

virus that carries DNA and infects bacteria

Question 43

What is the main difference b/w replication in prokaryotes and eukaryotes?

Answer 43

in prokaryotes the 2 replication forks meet when replication is complete

Question 44

Vertical gene transfer

Answer 44

from organism to its offspring

Question 45

Horizontal gene transfer

Answer 45

between organisms of the same generation