Biology Exam 4

Front 1

the location of a specific gene on a specific chromosome.

Back 1

A gene locus

Front 2

Gene

Back 2

heritable instructions for producing a trait.

Front 3

Diploid cells have 2 copies of every

Back 3

gene

Front 4

In a dihybrid cross, what is the probability of dominant, dominant?

Back 4

9/16

Front 5

In a dihybrid cross, what is the probability of dominant, recessive?

Back 5

3/16

Front 6

In a dihybrid cross, what is the probability of recessive, recessive?

Back 6

3/16

Front 7

Can environment alter phenotype?

Back 7

yes. In Siamese cats the enzyme that controls pigment productions is temperature sensitive.

Front 8

Do X-linked recessive disorders affect more males or females?

Back 8

males

Front 9

Initiation

Back 9

RNA Polymerase (Pol) interacts with DNA at the promoter (which typically contains a TATA box) and proteins associated with RNA Pol unwind the DNA helix

Front 10

Elongation

Back 10

RNA Pol moves along the DNA template (3’-5’) and adds nucleotides to the growing RNA strand (5’-3’) following the base pairing rules.

Front 11

Initiation Stage of Translation

Back 11

Mature mRNA transcript enters cytoplasm.

Initiator tRNA loaded onto small ribosomal subunit. This tRNA / small ribosomal subunit complex attaches to mRNA and moves along it scanning for a start codon (AUG).

Front 12

Elongation Stage of Translation

Back 12

Large ribosomal subunit attaches

tRNA corresponding to 2nd codon attaches

Covalent bond forms between amino acids

Ribosome release empty 1st tRNA

Ribosome shift down one codon allowing 3rd tRNA to bind

Polypeptide grows one amino acid at a time as one codon after enters ribosome (repeat steps 2-5)

Front 13

Termination Stage of Translation

Back 13

A STOP codon of the mRNA transcript enters the ribosome.

The mRNA transcript is released from the ribosome.

The newly translated polypeptide chain (protein) is released from the ribosome.

The ribosomal subunits separate.

Front 14

Amino acids are specified by a (#) letter code of nucleotides. Such a 3 letter code is called a ____.

Back 14

3, codon

Front 15

How many different amino acids are there?

Back 15

20

Front 16

How many codons are there?

Back 16

64

Front 17

Start codon

Back 17

AUG

Front 18

Stop codons

Back 18

UAA, UAG, UGA

Front 19

The genetic code links ____ to ____.

Back 19

mRNA, Protein

Front 20

A base substitution can: (3 things)

Back 20

alter a codon so that a different amino acid is coded for (this is called a missense mutation)

alter a codon, making it into a START or STOP codon (introduction of a stop codon is called a nonsense mutation)

have no effect because of the redundancy of the genetic code (e.g. CUU, CUC, CUA, and CUG all code for the amino acid leucine so changing the nucleotide at the third position of the codon would have no effect in this case)

Front 21

A base deletion (or addition) leads to a ____

Back 21

frameshift

Front 22

Transcription factors regulate ____ ___ _____ (3 words)

Back 22

eukaryotic gene expression

Front 23

Natural Selection is an _____. It is based on...

Back 23

algorithm, two undeniable facts that lead to one inescapable conclusion

Front 24

Fact 1 of Natural selection

Back 24

Individual Variation: Individuals in a population of any species vary in heritable traits. These variations arise as the result of random mutations in the genotype which lead to expressed variations in the phenotype (remember that the Central Dogma dictates that changes in phenotype will not affect the genotype).

Front 25

Fact 2 of Natural Selection

Back 25

Overproduction and Struggle for Existence: Any population of a species has the potential to produce more offspring than the environment can support. This leads to a struggle for existence, or competition.

Front 26

Inescapable conclusion of Natural Selection

Back 26

Individuals with traits (expressed random variations in phenotype) best suited to the local environment will have greater reproductive success and will pass on their successful traits to their offspring.

Front 27

The tree of life is more similar to a ______ with....

Back 27

bush, many twigs that represent the dead ends of failed evolutionary experiments

Front 28

Small molecules that inhibit the synthesis of bacterial macromolecules by targeting bacterial enzymes that are either distinct form thier eukaryotic counterparts or that are involved in pathways not found in eukaryotes

Back 28

Antibiotics

Front 29

prevents the cross-linking of small peptide chains in peptidoglycan, the main wall polymer of bacteria

Back 29

penicillin

Front 30

(found in antibiotic soaps) inhibits the enzyme that catalyzes the formation of cell wall lipids or fats

Back 30

Triclosan

Front 31

blocks the binding of tRNA to the ribosomal A-site

Back 31

Tetracycline

Front 32

prevents the transition of the ribosome from the initiation to elongation phase

Back 32

Streptomycin

Front 33

It typically takes less than ___ years and as little as _-_ years for resistant bacterial strains to appear following the introduction of a new antibiotic

Back 33

10, 1-2

Front 34

3 general ways bacteria can develop resistance through random mutations

Back 34

They can alter pumps used to remove toxins to also pump out the antibiotic (this typically leads to multi-drug resistance)

They can alter a protein used to degrade other molecules to destroy the antibiotic

They can alter the target of the antibiotic so that the target is no longer sensitive

Front 35

Why do random mutations occur frequently in the Influenza viruses?

Back 35

Their replication machinery does not have a proofreading function

Front 36

Incomplete Dominance

Back 36

Snapdragons.
Red + White = {ink
Dominant allele produces red pigment and recessive allele produces no pigment. Half as much red = pink.

Front 37

Codominance

Back 37

ABO blood typing
3 alleles, 2 of which are dominant
IA adds sugar A to cell
IB adds sugar B to cell
i adds nothing.

Front 38

Polygenic traits

Back 38

skin, hair color
Controlled by more than one gene

Front 39

Environmental effects

Back 39

temperature controls color in Siamese Cats

Front 40

Pleiotropy

Back 40

Control more than one trait
Hox genes control the pattern of the antero-posterior axis and the pattern of digits (fingers and toes)

Front 41

Incomplete Dominance

Back 41

Snapdragons.
Red + White = {ink
Dominant allele produces red pigment and recessive allele produces no pigment. Half as much red = pink.

Front 42

Codominance

Back 42

ABO blood typing
3 alleles, 2 of which are dominant
IA adds sugar A to cell
IB adds sugar B to cell
i adds nothing.

Front 43

Polygenic traits

Back 43

skin, hair color
Controlled by more than one gene

Front 44

Environmental effects

Back 44

temperature controls color in Siamese Cats

Front 45

Pleiotropy

Back 45

Control more than one trait
Hox genes control the pattern of the antero-posterior axis and the pattern of digits (fingers and toes)

Front 46

Linked Genes

Back 46

changes the results for a dihybrid cross. Usually we make assumption that genes are on separate chromosomes and can be segregated. But if they’re on the same chromosome, they can’t be segregated. Crossing over can mix and match the genes.

Front 47

Sex linked genes

Back 47

controlled by sex chromosomes

Front 48

The Central Dogma of Molecular Biology

Back 48

“Once information has passed into protein, it cannot get out again.” Francis Crick. One way street. So if you change the instructions, you change the protein. If you change the protein, you do not change the instructions.

Front 49

Transcription

Back 49

since you can’t take DNA out of nucleus, transcription photocopies it.

Takes place in the nucleus

A protein called RNA polymerase makes an RNA copy of a gene using complementary base pairings

Front 50

Translation

Back 50

Takes place in the cytoplasm, specifically on ribosomes (free floating or on RER).

mRNA (m = messenger) finds a ribosome which translates it using the genetic code.

Front 51

Non-Coding

Back 51

instructions for when & where genes are active

Front 52

These types of mutations can change the meaning of genes:

Back 52

• Alter a codon so that a different amino acid is coded for (this is called a missense mutation)
• Alter a codon, making it into a START or STOP codon (introduction of a stop codon is called a nonsense mutation)
• Have no effect because of the redundancy of the genetic code (e.g. CUU, CUC, CUA, and CUG all code for the amino acid leucine so changing the nucleotide at the third position of the codon would have no effect in this case)
• A base deletion (or addition) leads to a frameshift