6.2: Patterns of inheritance

Question 1

What are mutagens?

Answer 1

Increases the rate of mutations

Question 2

What are physical agents of mutagens?

3x

Answer 2

• X rays
• Gamma rays
• UV light

Question 3

What are chemical agents of mutagens?

3x

Answer 3

• Mustard gas
• Nitrous gas
• Benzopyrene (found in tobacco smoke)

Question 4

What are biological agents for mutagens?

Answer 4

• Some viruses
• Transposons
• Food contaminants

Question 5

What are persistent mutations?

Answer 5

Transmitted through many generations without change

Question 6

What are random mutations?

Answer 6

Not directed by a need on the part of the organism in which they occur

Question 7

What are five types of chromosome mutations?

Answer 7

• Deletion
• Inversion
• Translocation
• Duplication
• Non-disjuncture

Question 8

What is deletion?

Answer 8

Part of a chromosome, genes and regulatory seuqences, is lost

Question 9

What is inversion?

Answer 9

Sections of chromosome breakas off, turns 180 degrees and joins again
Some genes may be too far away from their regulatory nucleotides to be experienced

Question 10

What is translocation?

Answer 10

Piece of chromosome breaks off, then becomes attached to another chromosome - interferes with the regulation of the gene

Question 11

What is duplicaton?

Answer 11

Piece of chromosome is duplicated
Overexpression is harmful - too many of certain protiens/gene regulatory nucleic acids may disrupt the metabolism

Question 12

What is non-disjunction?

Answer 12

One pair of chromosome fails to separate leaving one gamete with an extra chromosome

Question 13

What is aneuploidy?

Answer 13

Chromosome number is not an exact multiple of the haploid number for that organism
Chromosomes/chromatids fail to separate during meiosis

Question 14

What is polyploidy?

Answer 14

Diploid gamete fertilised by a haploid gamete, the rsulting zygote will be triploid (three sets of chromosomes)

Question 15

How does genetic variation arise?

Answer 15

• Allele shuffling - swapping of alleles between non-sister chromatids, during crossing over in prophase 1
• Independent assortment of chromosomes - M1 AND A1
  Independent assortment of chromatids - M2 AND A2

Question 16

What does random fertilisation of gamtes that are already genetically unique produce?

Answer 16

Extensive genetic diversity among the resulting offspring

Question 17

What is random fusion?

Answer 17

Any gamete can potentially combine with any female gamete from an organism of the same species

Question 18

What are beneficial mutations?

Answer 18

Helped drive evolution through natural selection

Question 19

Why were blue eyes a beneficial mutation?

Answer 19

Help people see better in less bright light in temperate zones
BUT
Harmful in areas where sunlight intensity is higher as a lack of iris pigmentation could lead to lens cataracts

Question 20

Why was paler skin in temperate zones and darker skin in Africa benefical mutations?

Answer 20

High concentration of melanin protected early humans in Africa from sunburn and skin cancer
Temperate conditions: paler skin would be an advantge enabling vitamin D to be made with a lower intensity of sunlight - protects us from heart disease and cancer

Question 21

What are neutral mutations?

Answer 21

Neither harmful or benefical

• Inability to smell certain flowers
• Differently shaped ear lobes

Question 22

What are four types of variation?

Answer 22

• Interspecific
• Intraspecific
• Continuous
• Discontinuous

Question 23

What is interspecific variance?

Answer 23

Between two species

Question 24

What is intraspecific variance?

Answer 24

Within species

Question 25

What is variation caused by?

Answer 25

Genetic differences or the influence of the environment

Question 26

What is discontinuous variation?

Answer 26

Controlled solely by genetics | e.g human blood type

Question 27

What is continuous variation?

Answer 27

Caused by multiple genes and the environment working together e.g height/mass of an organism

Question 28

What are features of continuous variation?

Answer 28

* Presented in a histogram * No distinct categories * Data is quantitive

Question 29

What are features of discontinuous variation?

Answer 29

* Two or more distinct categories * No intermediates

Question 30

What is etiolation?

Answer 30

Elongation of stem between node, occurs in shaded area to reach light

Question 31

What is chlorosis?

Answer 31

Chlorophyll not produced

Question 32

What is monohybrid inheritance?

Answer 32

Involves the transmission of one gene from parents to their offspring

Question 33

Where does monohybrid inheritance occur?

Answer 33

Gametes (sex cells) because they are haploid, which means that they have one allele per gene

Question 34

What do you have to show before drawing punnet square? | 5 things

Answer 34

Parental genotypes: Rr x Rr Parental phenotypes: round round Gametes produced: Rr Rr F2 genotypes: * R R R r * R r r r F2 phenotypes: round round round round

Question 35

What is F1 generation?

Answer 35

The offspring from individuals with homozygous dominant and homozygous recessive genotypes All the offspring will be heterozygous, inheriting a recessive allele from one parent and a dominant allele from the other The offspring in the F1 generation will therefore all express the dominant trait in their phenotype

Question 36

What is the F2 generation?

Answer 36

Offspring from a two heterozygous F1 individuals It results in offspring exhibiting a 3:1 ratio of dominant to recessive phenotypes, as shown above.

Question 37

What is the genotypic ratio and phenotypic ratio for monohybrid inheritance?

Answer 37

Genotypic: 1:2:1 for RR:Rr:rr Phenotypic: 3:1

Question 38

What is dihybrid inheritance?

Answer 38

Inheritance of two genes therefore 4 alleles

Question 39

What can dihybrid crosses help to do?

Answer 39

* Determine whether genes are linked * Locate genes on specific chromosomes * Calculate expected phenotypic ratios in subsequent generations

Question 40

What is the ratio in dihybrid inheritance?

Answer 40

9:3:3:1

Question 41

What are reason why the ratio deviates in dihybrid inheritance?

Answer 41

Random fertilisation: * Gamete fusion is a chance process * Small sample sizes can lead to skewed ratios, while larger samples minimise these random effects Linked genes: * Linked genes are on the same chromosome so alleles are usually inherited together, maintaining the parents’ original allele combinations in offspring. * However, crossing over during meiosis can sometimes change these allele combinations by separating linked genes.