B5.1 Inheritance

Question 1

What is variation?

Answer 1

Differences within species.

Question 2

State four examples of variation.

Answer 2

• Height
• Build
• Eye colour
• Hair colour
• Blood group
• Language

Question 3

Name the two causes of variation within species.

Answer 3

• Genetics
• Environment.

Question 4

How can variation of a characteristic displayed be further categorised?

Answer 4

Into continuos vs. discontinuous variation.

Question 5

What is discontinuous variation?

Answer 5

• Variation that produces distint categories
• e.g. Eye colour, blood group, gender

Question 6

What is continuous variation?

Answer 6

• Variation that cannot be placed in distinct categories and instead produces a spectrum
• e.g. height, weight, skin colour

Question 7

What type of variation will human body mass display?

Answer 7

Continuous.

Question 8

What causes variation?

Answer 8

Mutations in the genetic code.

Question 9

What is asexual reproduction?

Answer 9

• Reproduction that produces a clone that is a genetically identical to it single parent.
• There is no mixing of genetic material

Question 10

Give two examples of organisms that can replicate asexually.

Answer 10

• Potato plants
• Stawberries
• Spider plants
• Bacteria
• Mushrooms
• Daffodils

Question 11

How does asexual reproduction take place?

Answer 11

Mitosis.

Question 12

What is sexual reproduction?

Answer 12

• Reproduction requiring two parents
• Genetic information is taken from both parents
• Organisms produce haploid gametes that fuse during fertilisation
• Offspring are not identical
• Results in variation

Question 13

Give one advantage and one disadvantage of sexual reproduction.

Answer 13

• Advantage: Variation in offspring leads to adaptation in a species. This results in some organisms within a species containing adaptations that allow them to cope with an environmental pressue. These organisms can reproduce, enabling the species/population to survive.
• Disadvantage: Reproduction requires two parents. Reproduction is slowers, so few offspring are produced.

Question 14

Give one advantage and one disadvantage of asexual reproduction.

Answer 14

Advantages

• If the parent was well adapted to an area then the offspring will share an identical set of characteristics
• Only one parent is needs - animals do not need to find a partner, plants do not require pollination.
• Faster, so large numbers of offspring are produced quickly

Disadvantage:

• Adverse changes to the biotic or abiotic factors may destroy the species, as all organisms affected due to the being no variation.

Question 15

What is a gamete?

Answer 15

• A sex cell
• Haploid cell used in sexual reproduction
• Sperm & egg
• Pollen & ovule

Question 16

What is a chromosome?

Answer 16

Tightly packaged DNA wrapped around histone proteins.

Question 17

What is a gene?

Answer 17

A section of DNA that can (but not always) code for a protein.

Question 18

What is an allele?

Answer 18

Different versions of the same gene e.g blue eyes vs. green eyes

Question 19

What is a dominant allele?

Answer 19

A version of a gene where only one copy is required for it to be expressed in the organisms phenotype.

Question 20

What is a recessive allele?

Answer 20

A version of a gene where two copies are required for it to be expressed in the organisms phenotype.

Question 21

What is meant by the phrase ‘pure breeding’?

Answer 21

The organism is homozygous for a characteristic.

Question 22

What is meant when an organism is homozygous?

Answer 22

When an organism has two copies of the same allele (either both dominant or both recessive).

Question 23

What is meant when an organism is heterozygous?

Answer 23

When an organism has two different version of the same gene (one dominan and one recessive).

Question 24

What is the genotype?

Answer 24

The genes present for a trait.

Question 25

What is the phenotype?

Answer 25

The visible characteristics displayed as a result of an organisms genotype.

Question 26

What is genome?

Answer 26

All of the genes present in an organism.

Question 27

What happens during fertilisation?

Answer 27

The nuclei of two haploid (n) gametes fuse to produce a single diploid (2n) cell known as a zygote.

Question 28

How are gametes made?

Answer 28

Meiosis.

Question 29

What are the stages of meiosis?

Answer 29

**Stage 1:** 1. The chromosomes are copied 2. The chromosomes line up upon the midline of the cell in pairs (one from the father, one from the mother) 3. Spindle fibres form 4. Spindle fibles contract towards the oppostive poles 5. One member of each pair is pulled to opposite ends of the cell - sections of DNA are often swapped at this stage (crossing over & recombination). 6. The cell divides in two form two separate cells **Stage 2:** 1. The chromosomes line up upon the midline of each new cell 2. Spindle fibres form 3. Spindle fibles contract towards the oppostive poles 4. The chromosomes are pulled in half - a single copy of each chromosome goes to the opposite end of the cell 5. Each cell divides in two. This results in four haploid (n), genetically diffenrent cells.

Question 30

Compare mitosis and meiosis.

Answer 30

**Mitosis** * The cell divides once * Two cells produced * Same number of chromosomes as parent cell * Used for growth & repair * Happens in all parts of the body * Daugther cells genetically identical to parent cell **Meiosis** * The cell divides twice * Four cells produced * Half the number of chromosomes as parent cell * Used to produce gametes * Happens in the gonads only (testes/ovaries) * Daugther cells genetically unique cells to parent cell

Question 31

What is the different between dipoild and haploid cells?

Answer 31

* Haploid cells have half the amount of genetic information as diploid cells * Haploid cells are germ (sex) cells * Diploid cells are somatic (body) cells

Question 32

What type of cell does meiosis produce?

Answer 32

Haploid germ cells e.g sperm and egg

Question 33

How are dominant alleles represented in a punnett square?

Answer 33

Uppercase letters

Question 34

How are recessive alleles represented in a punnet square?

Answer 34

* Lowercase version of the same letter as the dominant allele

Question 35

What is a mutation?

Answer 35

An alteration in the sequence of DNA bases.

Question 36

What is a mutagen?

Answer 36

* Substances or conditions that increase the chance of a mutation occuruing. * e.g. ionising radiation, benzene, ethanol, smoking

Question 37

Describe how a mutation in a coding DNA sequnece could be detrimental.

Answer 37

* DNA bases within the coding gene may be changes, added or deleted. * This changes the sequence of bases, therefore the order of base produced during transcription is altered. * This then alters the amino acids coded for in translation affecting the protein produced. * The protein produced may be the wrong protein, or fold incorectly and form a different shape * This change may affect the protein, particularly in specific molecules like enzymes and antibodies.

Question 38

Describe how a mutation in a non-coding DNA sequnece could be detrimental.

Answer 38

It may stop transcription and alter the expression of genes.

Question 39

State three negative examples of gene mutations.

Answer 39

* Huntington's disease * Sickle cell anaemia * Cystic fibrosis * Cancer * Alpha & Beta thalassemia * Tay-sachs disease * Phenylketonuria * Hemochromatosis * Marfan Syndrome

Question 40

State three neutral examples of gene mutations.

Answer 40

* Tongue rolling * Polydactyly * Joined ear lobes * Most mutations are neutral

Question 41

State three examples of beneficial gene mutations.

Answer 41

* Antibiotic resistance in bacteria * Colouring that aids camoflauge * De-pigmentation in cold/dark climates * Production of lactose post-infancy

Question 42

State three important findings of Gregor Mendel.

Answer 42

* Characteristics are determined by hereditary units (now refered to as genes) * Offspring recieve units from both paretns, one unit from each, so share traits with both paretns * Hereditary units are dominanr or recessive, so traits not always visible.

Question 43

What discovery lead to people accepting Mendel's ideas?

Answer 43

The discovery of the gene.

Question 44

Who captured the famous 'photograph 51'?

Answer 44

Rosalind Franklin.