Chromosomes, Genes & DNA

Question 1

Whats the structure of DNA?

Answer 1

DNA is made from 2 strands of molecules called nucleotides.
Each nucleotides contains a sugar molecule, a phosphate group and a nitrogen containing group called a base.

Question 2

How many bases are there in DNA?

Answer 2

There are 4 bases: adenine (A), thymine (T), cytosine (C), guanine (G)

Question 3

Whats the base pairing rule?

Answer 3

A binds to T because they form 2 hydrogen bonds.
C binds to G because they form 3 hydrogen bonds.

Question 4

Whats the template strand?

Answer 4

Only one of the strands of a DNA molecule actually codes for the manufacture of proteins in a cell.

Question 5

Whats a gene?

Answer 5

The sequence of triplets that codes for all the amino acids in a protein is a gene.

Question 6

What are the stages of protein synthesis?

Answer 6

DNA stay in the nucleus, but protein synthesis takes place in the cytoplasm.
This means for proteins to be made, the genetic code must be copied, and then transferred out of the nucleus into the cytoplasm.
This is carried out by a different type of nucleic acid called ribonucleic acid (RNA).

Question 7

Whats the difference between DNA and RNA?

Answer 7

1. DNA is double helix, RNA is single helix.
2. DNA contains the sugar deoxyribose, RNA contains ribose.
3. RNA contains the base uracil (U) instead of thymine (T).

Question 8

What occurs in protein synthesis?

Answer 8

The order of bases in the template strand of DNA forms the genetic code. The code is converted into the sequence of bases in the mRNA. In the cytoplasm the sequence of mRNA bases is used to determine the position of amino acids in a protein.

Question 9

Whats a gene mutation?

Answer 9

A change in the DNA of a cell. It can happen in individual genes or in whole chromosones. Sometimes, when DNA is replicating, mistakes are made.

Question 10

Whats a duplication mutation?

Answer 10

The nucleotide is inserted twice instead of once. The whole gene is different and will now code for an entirely different protein.

Question 11

Whats a deletion mutation?

Answer 11

A nucleotide is missed out. The whole gene is different and will now code for an entirely different protein.

Question 12

Whats a substitution mutation?

Answer 12

A different nucleotide is used. The triplet of the bases in which the mutation occurs is changed and it may code for a different amino acid.

Question 13

Whats a inversion mutation?

Answer 13

The sequence of bases in a triplet is reversed. This may or may not result in a different amino acid and altered protein structure.

Question 14

How many chromosomes do we have?

Answer 14

Nearly all human cells contain 46 chromosomes.
The cell from a male has 22 pairs of chromosomes and 2 that don’t form a pair - the X and Y chromosomes.
The cell from a female has 23 matching pairs including a pair of X chromosomes.

Question 15

Whats a homologous pair?

Answer 15

Pairs of matching chromosomes are called homologous pairs. They carry genes for the same features

Question 16

Whats a diploid cell?

Answer 16

Cells with chromosomes in pairs.

Question 17

Whats an allele?

Answer 17

Alleles are matching genes; one from our biological mother, one from our biological father. We have two copies of every gene.

Question 18

Whats a dominant allele?

Answer 18

Dominant alleles show their affects even if the individual only has one copy of the allele.

Question 19

Whats a recessive allele?

Answer 19

Recessive alleles only show their affect if the individual has 2 copies of the allele.