Inheritance and Genetics

Question 1

Why are new cells needed in an organism? (3)

Answer 1

Growth, replacing worn out cells, repairing damaged tissue

Question 2

Define allele?

Answer 2

Different form of the same gene

Question 3

Define gene?

Answer 3

A section of DNA that codes for a particular combination of amino acids which make a specific protein

Question 4

Define chromosome?

Answer 4

Genes grouped together

Question 5

Define mitosis?

Answer 5

Cell division in a normal body cell, produces two identical cells

Question 6

How does mitosis work?

Answer 6

Cell produces copies of the chromosomes in the nucleus, then divides once

Question 7

Define stem cell?

Answer 7

Unspecialised and undifferentiated cell found in early embryos

Question 8

Difference between animals and plants in terms of cellular differentiation?

Answer 8

Animals - differentiation only occurs in embryonic stage, so stops at maturity. Plants - cells don’t differentiate until they are in their final position in the plant, impermanent, can redifferentiate

Question 9

Why is animal cloning more difficult than plant cloning?

Answer 9

Animal cloning - cells differentiate permanently. Plants - undifferentiated cells always produce more

Question 10

What happens in meiosis?

Answer 10

Cell copies chromosomes so there are four sets, then divides twice in quick succession to form four gametes

Question 11

Why is each gamete produced in meiosis different from the others?

Answer 11

They contain random mixtures of the original chromosomal pairs. Introduces variety

Question 12

How is variation produced in sexual reproduction?

Answer 12

The combination of genes in the new pair of chromosomes contains alleles from each parent. One gamete from one parent will be different to another from the same.

Question 13

How to remember mitosis and meiosis?

Answer 13

MITosis - Making Identical Two

MEiosis - Making Eggs (and sperm)

Question 14

Difference between gametes and body cells?

Answer 14

Body cells have two sets of chromosomes; gametes only one

Question 15

Describe the process of stem cell manufacture?

Answer 15

Stem cells removed from early embryo and cultured/cultivated. Stem cells differentiate into different tissues, then are implanted into a body.

Question 16

Other than an embryo, where might stem cells be found?

Answer 16

Bone marrow, also in different tissues in the body; umbilical chords

Question 17

Problems with stem cells?

Answer 17

Ethical (embryos can’t give permission, taking human life); may cause cancer

Question 18

What does therapeutic cloning involve?

Answer 18

Using cells from an adult to proceed a cloned early embryo of themselves

Question 19

Why didn’t people believe Mendel’s findings?

Answer 19

They didn’t understand genes or chromosomes

Question 20

How is DNA composed?

Answer 20

Combinations of four different bases (ACTG) make up the long strands, grouped in threes, with each three coding for an amino acid

Question 21

Define homozygous

Answer 21

An individual with two identical alleles for a characteristic e.g. DD or dd

Question 22

Define heterozygous

Answer 22

An individual with different alleles for a characteristic, e.g. Dd

Question 23

Define genotype

Answer 23

Describes the genetic makeup of an individual regarding a particular characteristic, e.g. DD or Dd

Question 24

Define phenotype

Answer 24

The physical appearance of an individual regarding a particular characteristic, e.g. dimples or no dimples

Question 25

Difference between dominant and recessive alleles?

Answer 25

Dominant controls the development of a characteristic when one or both chromosomes have it (one or both parents). Recessive only controls such if it is present in BOTH chromosomes (i.e. both parents)

Question 26

Which gender does an XX sex chromosome determine?

Answer 26

Female (male is XY)

Question 27

What is polydactyly?

Answer 27

A genetic condition where a baby is born with extra fingers or toes, caused by a dominant allele

Question 28

What are the symptoms of cystic fibrosis? Is it caused by a dominant or recessive allele?

Answer 28

Organs are clogged by thick, sticky mucus and the reproductive system is affected, making the individual infertile in some cases

Question 29

Define a carrier (of cystic fibrosis)?

Answer 29

Someone who has a dominant healthy allele, but also a recessive cystic fibrosis allele. They have no symptoms, but their children have a 25% chance of getting it

Question 30

What are the chances of a child have polydactyly if a parent is heterozygous? And homozygous?

Answer 30

Heterozygous: 50% (half the gametes contain a faulty allele) Homozygous: 100%