Biology Genetics

Question 1

How are nucleotides connected to each other?

Answer 1

Nucleotides are connected to each via phosphodiester bonds.

Question 2

How are the complementary pairs of DNA strands held together? What are the consequences of these bonds?

Answer 2

The two complementary strands are held together via hydrogen bonds. There are two hydrogen bonds between the Adenine and Thymine. There are three hydrogen bonds between cytosine and guanine. Therefore, the more CG bonds a strand has, the more heat it will take to break the bonds.

Question 3

What is the result of having the phosphate backbone on the outside of the nucleotide?

Answer 3

The phosphate groups on the backbone of the DNA strands are negatively charged. As a result, the entire DNA molecule is considered to be negatively charged.

Question 4

Describe the steps of DNA replication.

Answer 4

A group of proteins called the replisomes bind the origin of replication sites along the DNA strand. DNA Helicase works to unwind the DNA Strand, DNA gyrase works to stabilize the supercoils, and Single stranded binding proteins work to stabilize each strand. Next, primase works to set RNA primers on the DNA in order for DNA polymerase to bind to the primers and begin the synthesis of DNA via phosphodiester bonds.

Question 5

Describe the direction in which the parent strand is copied and the new strand if formed.

Answer 5

The template, or parent strand, is copied in the 3 -> 5 direction. Because the parent is 3 - > 5 then the new strand is synthesized in the 5 -> 3 direction.

Question 6

What are the differences between DNA and RNA?

Answer 6

1. RNA contains the Ribose sugar instead of the Deoxyribose sugar.
2. RNA is single stranded unlike DNA which is double stranded.
3. RNA contains the base Uracil instead of Thymine.

Question 7

What are the two variations of chromatin and what is the purpose of each type?

Answer 7

The two types are heterochromatin and euchromatin. Heterochromatin is when the chromatin is tightly bound together so there can be no protein synthesis occur because of the tight interaction between the nucleotides. Euchromatin, on the other hand, is chromatin that is loosely bound together. Euchromatin allows for transcription factors to bind onto the dna to allow transcription to occur.

Question 8

What is Epigenetics?

Answer 8

Epigenetics are changes to the structure around the genome that effects the nucleotide sequences. For example, methylation of the nucleotide makes the strand tightly bind together. Epigenetics isn’t concerned with structural changes to the nucleotide sequence itself. Changes such as mutation is not an example of epigenetics.

Question 9

Where is DNA located in a eukaryotic cell?

Answer 9

In the nucleus and the mitochondria.

Question 10

What occurs in transcription?

Answer 10

Transcriptional factors bind to the promoter region of the DNA strand. From there, RNA polymerase acts on the strand to unzip it and then starts the process of elongation. RNA polymerase transcribes a RNA copy of the DNA in the 5’ -> 3’ direction. No proof reading occurs in transcription. A termination sequence will signal the end of the transcription process.

Question 11

In elongation, where does the amino acid bind to in the transfer rna?

Answer 11

3’ region of the transfer rna.

Question 12

Differentiate antisense, sense, template, and coding strands.

Answer 12

The strand which is transcribed is called the template, or antisense strand.
The strand which is not transcribed is called the coding, or sense strand.

Question 13

What is the purpose of post transcriptional processes?

Answer 13

1. protection in the cytosol.
2. Removal of introns
3. Help initiate the start of translation.

Question 14

What are the three features of post transcriptional modification?

Answer 14

1. Addition of poly a tail
2. Addition of 5’ cap
3. Removal of introns.

Question 15

What is the equation for calculating number of amino acid sequence?

Answer 15

20^n.

Question 16

What are the stop codons?

Answer 16

UAG, UGA, and UAA.

Question 17

What are the start codons?

Answer 17

AUG.

Question 18

Describe mutation and hereditary.

Answer 18

Mutation in somatic cells are not hereditary, however, mutations in germ cells are hereditary.
These mutations are either spontaneous or induced.

Question 19

Contrast transition and transverse mutations in genes?

Answer 19

Both are point mutations in the nucleotide sequence. A transition mutation is when a purine is changed for another purine, or when a pyrimidine is changed for another pyrimidine. A transversion mutation occurs when a purine is changed for a pyrimidine or a pyrimidine is changed to a purine.

Question 20

Describe a silent mutation.

Answer 20

A silent mutation has no noticeable change in the function of a protein. There is a change in the genome, but it doesn’t have any effect.

Question 21

Describe a missense mutation

Answer 21

A missense mutation occurs when a change in the sequence results in a change in the codon sequence. The change can either be neutral because it results in the same amino acid, OR the change in the amino acid during translation.

Question 22

Describe a nonsense mutation.

Answer 22

A nonsense mutation occurs when a stop codon is prematurely place in the sequence.

Question 23

Describe some chromosomal mutations.

Answer 23

Entire pieces of the chromosome can be mutated which has much more adverse effects then nucleotide mutations. Insertion of strands, deletion of strands, translocation of strands, inversion of strands, duplication of strands.

Question 24

What happens if a nondisjunction event occurs during Anaphase I vs Anaphase II?

Answer 24

If it occurs in anaphase 1 then two gametes will have 3 sets while the other two only have 1 set.

If it occurs in anaphase 2 then two gametes will be normal, 1 will have 3 sets, while the other has 1 set.

Question 25

Describe the process of spermatogenesis

Answer 25

First, spermatogonium undergoes mitosis to produce two diploid copies known as primary spermatocytes. Each primary spermatocyte undergoes the Meiosis I to produce 2 haploid cells called secondary spermatocytes. Each haploid cell undergoes Meiosis 2 in order to form 2 spermatids. In total, you will have 4 spermatids. Each spermatid will mature to form sperm cells.

Question 26

Describe the process of oogenesis

Answer 26

Before the female is born, the oogonium undergoes mitosis to produce two primary oocytes. The process is halted at prophase 1 until puberty. The primary oocyte undergoes meiosis 1 to produce secondary oocyte plus a polar body, which is discarded. The secondary oocyte is halted until it travels down the fallopian tube. The secondary oocyte completes meiosis two after being penetrated by a sperm cell. Meiosis 2 is completed forming an ovum and a polar body, which is discarded.

Question 27

What is the most important step in meiosis for genetic diversity?

Answer 27

Prophase I, when genetic rearrangement of the homologous chromosomes occur.

Question 28

What are the key factors in Hardy- Weinberg Equilibrium?

Answer 28

1. No natural selection.
2. No random mating.
3. No mirgration
4. No mutations
5. Large population

Question 29

Describe operons

Answer 29

Operons include both inducible and repressible systems, and offer a simple on–off switch for gene control in prokaryotes

Question 30

Describe the lac operon (inducible)

Answer 30

High concentrations of glucose, the repressor is transcribed to inhibit the transcription of beta galactasidase.

Low concentrations of glucose means high concentrations of lactose. The repressor is inactivated and the beta galactasidase is transcribed.

Question 31

Describe trp operon (repressible)

Answer 31

When trp is high then it acts as a copressor stopping transcription.

When trp is low then transcription continues.

Question 32

Describe histone methylation

Answer 32

Adding methyl groups to silence DNA trasncription

Question 33

Describe histone acetylation

Answer 33

Adding acetyl groups to allow for DNA trasncription