Genetics 2.2

Question 1

What is DNA made out of?

Answer 1

DNA is a polynucleotide made up of lots of nucleotides joined together. Each nucleotide is made from a pentose sugar (5 carbon atoms), a phosphate group and a nitrogenous base.
The sugar in DNA nucleotides is deoxyribose sugar

Question 2

What are the 4 possible bases?

Answer 2

A, T, C, G

Question 3

What do two polynucleotide strands join together to form?

Answer 3

A double helix

Question 4

What is the structure DNA?

Answer 4

A phosphate group attached to a sugar (deoxyribose sugar) attached to a base. The base is the thing that changes.

Question 5

What bond do two polynucleotides join together to make?

Answer 5

Hydrogen bonds

Question 6

Describe how DNAs structure makes it good at its job.

Answer 6

DNA molecules are very long and are coiled up very tightly, so a lot of genetic information can fit into a small space in the cell nucleus.
DNA molecules have a paired structure, which makes it much easier to copy itself.
Double helix makes it very stable.

Question 7

How is DNA stored in eukaryotic cells?

Answer 7

Eukaryotic cells contain linear DNA molecules that exist as chromosomes (thread-like structures) each made up of one long molecule of DNA. The DNA has to wound around proteins (histones).
The DNA (and protein) is then coiled up very tightly to make a compact chromosome.

Question 8

How do DNA molecules in prokaryotic cells differ from those in eukaryotic cells?

Answer 8

DNA molecules in prokaryotic cells are also carried as chromosomes, but the DNA molecules are shorter and circular.
The DNA isn’t wound around proteins, it condenses to fit in the cell by supercoiling.

Question 9

What do genes code for?

Answer 9

Proteins (polypeptides)

Question 10

How many bases code for an amino acid?

Answer 10

3

Question 11

What are exons and introns?

Answer 11

Exons: sections of DNA that code for amino acids
Introns: sections of DNA that don’t code for amino acids

Question 12

When are introns removed?

Answer 12

During protein synthesis

Question 13

Give an example of a flow chart to show how DNA determines our nature and development.

Answer 13

DNA sequence Proteins and Enzymes enable Metabolic
Determines Enzymes Metabolic Pathways
Amino acid —> Formed —–> pathways ——-> determine
Sequence Nature and
development

Question 14

What are mutations, and what can they produce?

Answer 14

Mutations are changes in the base sequence of an organisms DNA. So, mutations can produce new alleles.

Question 15

What do gametes join together to form in fertilisation?

Answer 15

A zygote

Question 16

What is the diploid number for normal body cells?

Answer 16

2n

Question 17

Name a haploid cell

Answer 17

Sperm, egg

Question 18

What is the haploid number of chromosomes?

Answer 18

n

Question 19

How many gametes are formed in meiosis?

Answer 19

4

Question 20

Outline the steps of meiosis.

Answer 20

The DNA unravels and replicates itself, so there are two copies of each chromosome.
The DNA condenses to for double armed chromosomes made two sister chromatids.
Meiosis 1 the chromosomes arrange into homologous pairs, the pairs then separate, halving the chromosome number.
Meiosis 2, the pairs of sister chromatids that make up each chromosome are separated, four haploid cells that are genetically different are formed.

Question 21

How does meiosis produce cells that are genetically different.

Answer 21

1. Crossing over of chromatids

2. Independent segregation

Question 22

What is a genetic bottleneck?

Answer 22

An event that causes a big reduction in population, which reduces the number of different alleles in a population.

Question 23

Name a type of bottle neck.

Answer 23

The founder effect. It describes what happens when a few organisms from a population start a new colony.only a small number of organisms have contributed to the gene pool.

Question 24

What is selective breeding?

Answer 24

When humans selectively reproduce to organisms together in order to produce higher yielding breeds. Once an organism with the desired characteristics has been produced, only that type of organism will continually be bred. This reduces the number of alleles in the gene pool.

Question 25

What are the pros and cons of selective breeding?

Answer 25

Pros: high yielding plants and animals
Can be used to produce organisms with an increased resistance to disease. (So farmers use fewer drugs/pesticides)
Increased tolerance of bad conditions
Cons:can cause health problems, lower life expectancy
Reduces genetic diversity.