B5.1 - Inheritance

Question 1

Phenotype

Answer 1

Appearance of an organism

Question 2

Variation

Answer 2

Differences within a species

Question 3

Two type/causes of variation:

Answer 3

• genetic variation (genetic material inherited from parents)
• environmental variation (environment in which you live in)

Question 4

Characteristics causes by genetic variation:

Answer 4

• eye colour
• blood group
• genetic disorders

(Caused by genes)

Question 5

Characteristics caused by environmental & genetic variation

Answer 5

• height

- weight

Question 6

Characteristics caused by environmental variation

Answer 6

• intelligence
• language spoken
• good swimmer

Question 7

Discontinuous variation

Answer 7

• characteristics fall into distinct groups
• genetic variation
• controlled by 1/2 genes
• display in bar chart

(Eg. Gender, eye colour, blood type)

Question 8

Continuous variation

Answer 8

• takes any value in a range
• genetic & environmental variation
• controlled by multiple genes
• display in histogram

(Eg. Leaf surface area, skin colour)

Question 9

Asexual reproduction

Answer 9

• requires only 1 parent
• replicate their genetic material and divide by mitosis
• no mixing of genetic material
• each new organism genetically identical to parent cell (clone)
  Eg. Bacteria

Question 10

What organisms can reproduce asexually

Answer 10

• potato plants
• spider plants
• daffodils
• sea anemones
• star fish
• bacteria

Question 11

Sexual reproduction

Answer 11

• requires 2 parents
• offspring not identical as genetically information taken from both parents
• results in variation (unique genome)
  Eg. Most animals/plants

Question 12

describe sexual reproduction in animals

Answer 12

• organisms produce sex cells = gametes (male: sperm, female: ova)
• gametes fuse together in fertilisation
• fertilised egg develops into offspring

Question 13

Describe sexual reproduction in plants

Answer 13

• pollen cell (male sex cell) fuses with egg cell (female sex cell) in ovule
• to create new seed, will grow into plant

Question 14

Advantages of asexual reproduction

Answer 14

• if parent well adapted to area,m offspring will share identical characteristics
• only 1 parent needed (animals don’t need to find partner, plants don’t require pollination) = faster reproduction

Question 15

Disadvantages of asexual reproduction

Answer 15

• adverse changes to biotic/abiotic factors may destroy species, all organisms will be affected as no variation

Question 16

Advantages of sexual reproduction

Answer 16

• variation in offspring leads to adaptations in species, some organisms contain adaptations required to cope with environmental pressure, can reproduce so population of species can continue

Question 17

Disadvantages of sexual reproduction

Answer 17

• requires 2 parents = slower reproduction so few offspring produced

Question 18

Diploid cells

Answer 18

• Normal body cells
• contain 2 sets of each chromosome
• contain 46 chromosomes

Question 19

Haploid cells

Answer 19

• eg. Ova & sperm cells
• have 1 of each chromosome
• contain 23 chromosomes

Question 20

What happens during fertilisation

Answer 20

• 2 haploid gamete cells join together forming a diploid cell (zygote)
• zygote divides many times by mitosis to produce new organism
• unique combination of genes in new organism as mixture of parents genetic material

Question 21

Genome

Answer 21

All genetic material present in an organism

Question 22

How are gametes produced

Answer 22

• By meiosis (type of cell division)
• 4 haploid cells produced from 1 diploid parent cell
• occurs in ovaries to produce ova & testes to produce sperm

Question 23

First stage of meiosis

Answer 23

• chromosomes in diploid cells copied
• chromosomes line up along middle of cell in pairs
• members of each pair pulled to opposite ends of cell (sections of DNA swapped)
• cell divides in two
• two separate cells formed

Question 24

Second stage of meiosis:

Answer 24

• chromosomes line up along middle of each of 2 new cells
• each chromosome pulled in half
• single copy of each chromosome goes to opposite ends of cell
• each cell divides in two
• four new haploid cells made, each genetically different from each other & parent cell

Question 25

Alleles

Answer 25

Different forms of a gene

Question 26

Dominant allele (B)

Answer 26

Version of a gene whose characteristics is always expressed if present in genome, only 1 copy needed

Question 27

Recessive allele (b)

Answer 27

Version of a gene whose characteristic only expressed if 2 copes are present in genotype

Question 28

Genotype

Answer 28

Combination of alleles present in an organism

Question 29

3 types of genotypes

Answer 29

- homozygous dominant (BB) - homozygous recessive (bb) - heterozygous (Bb)

Question 30

How did Gregor Mendel discover how characteristics are inherited

Answer 30

- carried out experiments using pea plants - pea plants can produce pods that are green/yellow - green = dominant, yellow = recessive

Question 31

Why does the father determine the sex of its offspring

Answer 31

Male gametes can have either an X or Y chromosome whereas all female gametes contain an X chromosome 23rd pair of chromosomes = sex chromosomes: Female = XX Male = XY

Question 32

Mutation

Answer 32

When the sequence of DNA bases is altered

Question 33

Genetic variant

Answer 33

- Different version of an allele, caused by change in DNA | - all arise from mutations

Question 34

What determines the effect the mutation will have on an organism

Answer 34

The position of the mutation in the DNA sequence

Question 35

What affects do mutations have on an organism

Answer 35

- most mutations won’t affect organism’s phenotype - some mutations may influence organisms phenotype - few mutations will determine organism’s phenotype, lead to variation within a species

Question 36

Harmful mutations cause:

Answer 36

- cancer (cells grow & divide uncontrollably) - production of abnormal protein channels (allow molecules to transport through cell membrane) that don’t function properly (eg. cystic fibrosis) - different shaped protein molecules (eg. sickle cell anaemia = unusually shaped haemoglobin molecules, blood cells sickle shaped)

Question 37

Give an example of a neutral mutation (no benefit or harm)

Answer 37

Ability to roll your tongue

Question 38

Give an example of a beneficial mutation

Answer 38

Mutations in some bacteria enable them to be resistant to antibiotics, increases chance of survival

Question 39

How can mutations alter an organism’s phenotype, what can this lead to

Answer 39

- in gene, DNA bases may be changed, added, deleted = changes sequence of bases - order of bases in mRNA (transcription) different = different order of amino acids = wrong protein produced / fold incorrectly - if mutation occurs in non-coding section of DNA (triggers process of transcription), gene may not be transcribed into mRNA = proteins won’t be produced

Question 40

What may happen as a result of the proteins not being produced properly due to mutations

Answer 40

- if protein is an enzyme, active site may change shape - can no longer bing to substrate & catalyse specific chemical reactions - results in metabolic diseases (eg. phenylketonuria, PKU = phenylalanine can’t be broken down by body = brain damage)

Question 41

Give the years & stages of the history of genetics

Answer 41

1866: Discovery that certain characteristics are inherited 1869: Nuclein discovered 1944: Genes can be transferred from 1 generation to next 1950: DNA base pairs discovered 1952: DNA crystals photographed 1953: Double-helix structure of DNA identified 1953-2000: Advances in genetics 2003: Human genome project complete

Question 42

Describe Gregor Mendel discoveries in 1866

Answer 42

Carried out experiments on peas, noticed that: - characteristics in plants were determined by hereditary units (now called genes) - hereditary units are passed on from both parents, 1 unit from each - hereditary units are dominant or recessive