10 The Nature of the Gene and the Genome

Question 1

What is a Genome?

Answer 1

The collective body of genetic information in an organism

Question 2

What is the unit of inheritance?

Answer 2

Gene

Question 3

Describe 3 properties of an allele.

Answer 3

1. Each trait is controlled by two alleles
2. Alleles can be identical or different
3. The dominant allele masks the recessive

Question 4

A gamete contains ___ gene for each trait.
The union of a male and a female gamete forms a ___.
__ alleles are inherited for each trait.

Answer 4

One
Somatic cell
Two

Question 5

Genes on the same chromosome are part of the same ___ and do not ____.

Answer 5

Linkage group, assort independently

Question 6

What is the physical carrier of genes?

Answer 6

Chromosome

Question 7

Gametes has __ copy/copies of each chromosome.

A somatic cell has ___ copy/copies of each chromosome.

Answer 7

One.

Two.

Question 8

What happens during meiosis?

Answer 8

Pairs of homologous chromosomes separate into different cells. Gametes are produced after division. Number of chromosomes is halved.

Question 9

What happens during mitosis?

Answer 9

Chromosomes double in parent cell and each daughter cell contains the same number of copies as parent cell.

Question 10

Describe the structure of a nucleotide.

Answer 10

Consists of a phosphate, a pentose sugar, and either a pyrimidine or purine nitrogenous base.

Question 11

What are the four different bases in DNA? Classify into purines and pyrimidines. Which ones bond with which ones?

Answer 11

Purines: Adenine, Guanine
Pyrimidines: Cytosine, Thymine
G bonds with C, A bonds with T

Question 12

Chargaff’s rules states that…

Answer 12

Number of A = Number of T, Number of C = Number of G

Question 13

Describe the Watson-Crick model of the DNA.

• Structure
• What’s inside and what’s ouside
• Dimensions
• What type of bonding holds the structure?
• How many of such bonding between each base pair?

Answer 13

1. Two chains of anti-parallel nucleotides spiraling around each other, one going from 5’ to 3’, and one going from 3’ to 5’. The two chains are complementary (base pairs)
2. Sugar-phosphate backbone on the outside, bases on the inside
3. 2 nm wide, 1 turn for every 10 pairs of bases (36 degrees between each base)
4. Hydrogen bonds hold purines with pyrimidines
5. 3 in G and C, 2 in A and T

Question 14

Importance of the Watson-Crick model of the DNA

-3 major points

Answer 14

1. Storage of genetic information: DNA is the code for amino acid sequences in proteins
2. Replication and inheritance: DNA contains information for synthesis of new DNA
3. Expression of the genetic message: DNA must be expressed

Question 15

What is DNA denaturation? Renaturation/Reannealing?

Answer 15

Denaturation: separation of DNA into two strands
Renaturation: single stranded DNA reassociate into double strand

Question 16

Given a graph of relative absorbance and temperature for a DNA, how would you determine the melting temperature?

Answer 16

It is the half way point on the portion of the curve where there’s a sharp change in absorbance.

Question 17

How does G:C content influence the melting temperature of a DNA?

Answer 17

Higher G:C content increases melting temperature. G:C pairs have an extra hydrogen bond compared to A:T

Question 18

Experiments done by Avery, MacLeod, McCarty as well as experiments by Hershey and Chase confirmed that ____, not ____, is the genetic material.

Answer 18

DNA, protein