3.1 Genes

Question 1

What is an allele?

Answer 1

Different forms of the same gene.

For example, a gene for eye color can have different alleles, such as blue colored eyes and brown colored eyes.

Question 2

What are mutations?

Answer 2

Changes in the sequence of DNA.

This can be favorable, neutral, or harmful.

Example: Albinism

Question 3

What is a locus?

Answer 3

The specific location of a gene on a chromosome.

Question 4

What is homozygous?

Answer 4

Two copies of the same allele.

Example: Both alleles for eye color are brown.

Question 5

What is heterozygous?

Answer 5

Two different alleles of the same gene. Mixed alleles.

Example: Black allele and a brown allele for eye color gene.

Question 6

What is a genotype?

Answer 6

The alleles of a gene.

For example: Bl(black) and Br(brown), both are alleles for the eye color gene.

Question 7

What is a phenotype?

Answer 7

The physical characteristic that results from your genes.

Example: The result of a Br and Bl genotype is black eye color.

Question 8

What is base-substitution mutation?

Answer 8

A mutation that changes one nitrogenous base in a sequence.

For example: Guanine is substituted for adenine, this changes the outcome of the gene.

Question 9

Explain sickle cell anemia.

Answer 9

• Sickle cell anemia is a mutation in the hemoglobin base sequence.
• Normal hemoglobin reads GAG and forms glutamic acid.
• Sickle cell (mutated hemoglobin) reads GTG which results in the formation of a protein known as valine.
• The mutation causes a change in the base sequence of mRNA.
  
  • Normal is read as GAG and sickled is read as GUG.

Question 10

What are the steps you would take to compare organisms?

Answer 10

1. Go to NCBI
2. Type the name of the gene or organism.
3. Click on the result.
4. Scroll down to mRNA sequence link.
5. Click on fasta, to get the sequence.
6. Go to blast
7. Paste the sequence of mRNA and you will get the result.

Question 11

What is the blast website used for?

Answer 11

• How closely or distantly related organisms are
• Comparing different organisms

Question 12

Compare a named species with more genes than humans.

Answer 12

Rice:

• Genes: 35000
• Base pairs: 400 million
• Diploid number of chromosomes: 24

Humans:

• Genes: 20000
• Base pairs: 3200 million / 3.2 billion
• Diploid number of chromosomes: 46

Question 13

Compare a named species with fewer genes than humans.

Answer 13

Yeast:

• Genes: 6000
• Base pairs: 12 million
• Diploid number of chromosomes: 32

Question 14

Compare a named bacterial species’ genes with humans.

Answer 14

E Coli:

• Genes: 4000
• Base pairs: 5 million
• Diploid number: Non / 1n

Question 15

Compare a named plant species genes with a human.

Answer 15

Wheat

• Genes: 100,000
• Base pairs: 16000 million
• Diploid number of chromosomes: 42