Genetics Final: Midterm 1 Questions

Question 1

Heat can disrupt hydrogen bonding between DNA strands. Which of the following DNA strands would denature at the HIGHEST temperature?

Answer 1

Whichever one has the largest number of GC bonds.
This is due to the fact that GC are connected by 3 hydrogen bonds unlike AT which are connected by 2 hydrogen bonds.
This means it takes more energy and a higher temperature to denature strands with more GC bonds.

Question 2

If a DNA molecule contains 17% guanidine bases (G), then what percentage of thymine bases will it have?

Answer 2

33%
Because G binds to C they have equal amounts.
So 17 + 17 = 34
100 - 34/2 = 33
So there are 33% of each Thymine and Adenine within the molecule.

Question 3

If the sequence of one strand of DNA is
5’ -GCTAGCGTCG-3’,
what is the sequence of the complementary strand?

Answer 3

3’-CGATCGCAGC-5’

Question 4

All DNA polymerases synthesize new DNA by adding nucleotides to the ____ of the growing DNA chain.

Answer 4

3’ OH

Question 5

Know the DNA replication fork.

Answer 5

:)

Question 6

What is the function of telomerase?

Answer 6

Adds repetitive DNA to protect chromosome ends

Question 7

What is the function of DNA polymerase I?

Answer 7

Removes RNA primer and replaces DNA

Question 8

What is the function of DNA polymerase III?

Answer 8

Synthesizes most of the new DNA strand

Question 9

What is the function of RNA primase?

Answer 9

Synthesizes a fragment of RNA to initiate synthesis

Question 10

What is the function of DNA ligase?

Answer 10

Glues fragments of single-stranded DNA together

Question 11

Which of the RNAs have the message for an encoded protein?

Answer 11

mRNA

Question 12

Which of the RNAs carry free amino acids to the ribosome?

Answer 12

tRNA

Question 13

Which is a true statement regarding transcription in most organisms?

Answer 13

Different genes may be transcribed from different strands of DNA.

Question 14

Where are promoters usually located?

Answer 14

Upstream of the start site

Question 15

In transcription, where are new nucleotides always added onto the growing DNA chain?

Answer 15

The 3’ OH

Question 16

Which of the following statements about RNA polymerase is NOT true?

Answer 16

RNA polymerase reads a template strand of DNA 5’ to 3’

Question 17

All of the following are true statements regarding RNA polymerase:

Answer 17

• RNA polymerase adds a ribonucleotides to the 3’ end of a growing RNA molecule.
• RNA polymerase binds to a promoter to initiate transcription
• During transcription of a gene, RNA polymerase reads only one strand of DNA.
• RNA polymerase has many subunits

Question 18

If the DNA strand 5’-GTACCGTC-3’ were used as template for transcription, what would the sequence of the transcribed RNA?

Answer 18

5’-GACGGUAC-3’

Question 19

If the sequence of an RNA molecule is 5’-GGCAUCGACG-3’, what is the sequence of the coding strand of DNA?

Answer 19

5’-GGCAUCGACG-3’

Question 20

Go over question 20 on paper.

Answer 20

:)

Question 21

In eukaryotic cells, where do “specific” transcription factors bind?

Answer 21

The regulatory promoter and the enhancer.

Question 22

What would the consequence by of a two nucleotide-deletion mutation in the middle of the first exon of a protein-coding gene?

Answer 22

A reading frameshift would occur. All codons (and thus amino acids) downstream of the codon in which the deletion occurred would be different including the stop signal.

Question 23

Be able to read codon charts and interpret them.

Answer 23

:) refer to questions 23-24 on the first exam.

Question 24

Haploid cells are cells with _____ chromosomes.

Answer 24

A single set.

Question 25

In Labrador retrievers, black coat color is dominant to brown. Suppose that a black Lab is mated with a brown one and the offspring are four black puppies and one brown puppy. What can you conclude about the genotype of the black parent?

Answer 25

The genotype must be Bb.
We know the black parent is heterozygous since there was a brown puppy in the f1 progeny.
If the parent was heterozygous dominant, there would be no brown puppies. He also cannot be heterozygous recessive considering that he shows the black phenotype so we know he must have at least one big B.

Question 26

In Mendel’s peas, yellow seeds are dominant to green. A pure-breeding yellow plant is crossed with a pure-breeding green plant. All of the offspring are yellow. If these yellow offspring are allowed to self-fertilize, what will the expected proportion of plants with green seeds in the next generation?

Answer 26

25%

Question 27

Refer to 28 on midterm 1.

Answer 27

:)

Question 28

In animals, the inability to make the pigment melanin results in albinism, a recessive condition. Two unaffected parents, who have decided to have three children, have a first child that has albinism (genotype aa). What is the probability that the seconds and third children will also have albinism?

Answer 28

1/16 
Review the formula for this. 
Total factorial!
over 
affected factorial/unaffected factorial
???

Question 29

Round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). A true-breeding pea plant with round and yellow seeds is crossed to a true-breeding plant with wrinkled and green seeds.
The f1 progeny are allowed to self-fertilize. What is the probability of obtaining a wrinkled, yellow seed in the f2?
What is the probability of obtaining a round yellow seed?

Answer 29

3/16

9/16

Question 30

Review pedigrees.

Answer 30

:) Questions 33-37