Chapter 18: Genes & inheritance

Question 1

What are genes?

Answer 1

Genes are sections of DNA that determine a particular feature…

…by instructing cells to produce particular proteins

Also defined as “part of a chromosome that determines a particular feature”.

Question 2

Who was Gregor Mendel?

Answer 2

A monk from Czech Republic who published ground-breaking research in 1865 that uncovered the basic rules of how features are inhereted:

• a gene is passed from one generation to the next
• genes can have different forms (alleles)
• each individual must have two alternate alleles per feature
• the sex cells only have one allele per feature
• one allele can be dominant over another

​Considered v radical at the time and went against the ideas of the time

Question 3

What is a test cross?

Answer 3

A test to find out the genotypes of the parents

Question 4

Can you draw an example of a test cross?

Answer 4

Question 5

What is a genotype?

Answer 5

a genotype describes the alleles each cell has for a certain feature

Question 6

What is a phenotype?

Answer 6

a phenotype is the feature that results from the genotype (e.g. a tall plant)

Question 7

What’s the difference between

a dominant and a recessive allele?

Answer 7

There are two alleles of each gene

One allele is dominant over the other allele, which is recessive

When two different alles (one dominant one recessive) are in the same cell….the dominant allele is expressed (allowed to ‘work’)

An individual can have two dominant alleles, two recessive alleles or and dominant and a recessive allele in each cell

Question 8

Homozygous or heterozygous?

Answer 8

Alleles are different versions of the same gene.

An allele can be dominant or recessive. Individuals, meanwhile, can be homozygous or heterozygous:

• individuals who are homozygous for a certain gene carry two copies of the same allele
• individuals who are heterozygous for a certain gene carry two different alleles

A recessive characteristic will only be shown if an individual is homozygous for the recessive allele. A dominant characteristic will be shown even if an individual is heterozygous for the dominant allele.

Question 9

Writing our and presenting genetic information…

Answer 9

…am really sorry, its quite detailed and think you’re better off looking at the text book…pages 202-205

Question 10

Can you answer these questions???

Answer 10