Cell Division & Genetics - Part 2

Question 1

Much of our understanding of inheritance comes from the work of an Austrian monk called Gregory Mendel. During his investigations he noticed that some characteristics were more common than others and that they were more likely to be found in the offspring. What did he call these two types of characteristics?

Answer 1

Dominant and recessive

Question 2

What is the term used to describe the letters describing the characteristics?

Answer 2

Genotype

Question 3

What is the term used to describe the outward appearance of the genotype?

Answer 3

Phenotype

Question 4

What is genetics?

Answer 4

Genetics is the study of inheritance i.e. how characteristics are passed from one generation to the next.

Question 5

How many chromosomes are in each human cell?

Answer 5

46

Question 7

What are chromosomes?

Answer 7

Chromosomes are located in the nucleus of cells and carry the genetic material in short sections called genes.

Question 9

What is a gene?

Answer 9

A gene is a short section of chromosome that codes for a particular characteristic, e.g. eye colour

Question 10

What is an allele?

Answer 10

An Allele is a particular form of a gene. For example, brown eyes and blue eyes are different alleles of the eye colour gene.

Question 11

What does homozygous mean?

Answer 11

The term homozygous is used to describe where both alleles of a gene are the same. For example, in eye colour both alleles are for brown eyes.

Question 11

What does the term heterozygous mean?

Answer 11

Heterozygous is used to describe alleles of a gene that are different. For example, in eye colour one allele is for brown eyes and the other is for blue eyes.

Question 11

What is the genotype?

Answer 11

The genotype is paired symbol showing the allele arrangement in an individual.

Question 11

What is the phenotype?

Answer 11

The phenotype is the outward appearance of an individual. In other words, the characteristics we can see.

Question 12

What is the name given to parent plants that only produce one type of offspring?

Answer 12

Pure breeding

Question 13

What is meant by a dominant allele?

Answer 13

In the heterozygous condition the dominant allele overrides the non-dominant (recessive) allele. In other words, it is always expressed (shows its effects)

Question 14

What is a recessive allele?

Answer 14

A recessive allele is dominated by the dominant allele - it only shows itself in the phenotype if there are two recessive alleles.

Question 15

What is the complete set of chromosomes known as?

Answer 15

A karyotype

Question 16

What are Punnett Squares?

Answer 16

Punnett Squares are diagrams that are used to show the possible outcomes of genetic crosses. They can tell us the probability of a certain genotype being found in offspring.

Question 17

Explain why some genetic disorders are sex linked.

Answer 17

The X and Y chromosomes are not only responsible for sex determination, they also have the genes that code for conditions such as haemophilia and red/green colour blindness. These are referred to as sex linked.
Both cases the normal gene is dominant and these conditions are recessive and carried on the X chromosome. This is particularly important in males as they have only one X chromosome, therefore any recessive allele carried on this chromosome will show its effect in the phenotype, in other words the males will suffer from the condition. The female usually has a normal allele to mask the affect of the defect one and so females rarely suffer from sex linked conditions.

Question 18

What is the term used to describe a girl who is heterozygous for colour blindness?

Answer 18

A carrier