ch13 Heredity

Question 1

What is a gene?

Answer 1

1. unit of inheritance
2. made of sequence, nucleotides
3. part of, DNA molecule
4. codes for a single polypeptide.

Question 2

What are alleles?

Answer 2

1. Alternative forms, gene
2. occupy same genetic locus
3. code, different variants, same polypeptide
4. hence give rise, variation, phenotype

Question 3

Provide an example of alleles in rabbits.

Answer 3

In a certain species of rabbits, one allele codes for black fur (B) and another for brown fur (b).

Question 4

What is a homologous chromosome?

Answer 4

• pair chromosomes
• one is paternal
• other maternal in origin
• having same shape, length, same genes occupying same genetic loci, same centromere position

Question 5

Define genotype.

Answer 5

Genetic make-up of an individual.

Question 6

Define phenotype.

Answer 6

Observable trait of an individual.

Question 7

What does homozygous mean?

Answer 7

1. An individual having identical alleles of a single gene.
2. Individual could be homozygous dominant/homozygous recessive

HD -> possess only copies of dominant allele
HR -> possess only copies of reccessive allele

Question 8

What is the difference between homozygous dominant and homozygous recessive?

Answer 8

HD
possesses only copies of the dominant allele

HR
possesses only copies of the recessive allele.

Question 9

Define heterozygous.

Answer 9

An individual having different alleles of a single gene.

Question 10

What is complete dominance?

Answer 10

1. allele, complete dominance, other alleles
2. suppresses effect, recessive allele
3. dominant allele, fully expressed, manifested, phenotype, homozygous
   dominant, heterozygous individuals.

Question 11

What is co-dominance?

Answer 11

1. allele, codominant w/ another allele of same gene
2. equally expressed, manifested -> phenotype, heterozygote.

Question 12

Define recessive allele.

Answer 12

• allele, suppressed by effects, dominant alleles
• only expressed, phenotype homozygous recessive individuals.

Question 13

Why do observed ratios often differ from expected ratios?

Answer 13

1. Expected ratios, calculated probabilities, based off theoretical model
2. Observed ratios -> random chance
3. as sample size increases, observed ratios become closer, expected ratios.

Question 14

Explain the inheritance of ABO blood group phenotypes.

Answer 14

ABO blood types,
controlled 1 gene, 3 alleles
- Ia, Ib, Io,
- co-dominance, multiple (>2) alleles.
- Ia Ib codominant
- Io recessive to Ia Ib

Question 15

What is the chromosomal composition of human females?

Answer 15

Human females
- 22 pairs autosomes,
- 1 pair sex chromosomes
- 2 X chromosomes

Question 16

ovum what chromosomes

Answer 16

ovum produced, female
all ovum, only contain X chromosome

Question 17

What is the chromosomal composition of human males?

Answer 17

Human males
- 22 pairs autosomes,
- 1 pair sex chromosomes
- 1 X 1 Y chromosome

Question 18

all sperm what chromosomes

Answer 18

sperm produced, male
half sperm cells, X chromosome,
other half sperm cells, Y chromosome,

Question 19

how is human female made from sperm, egg

Answer 19

• sperm cell containing X chromosome, fertilise ovum
• offspring possess 2 X chromosomes
• female

Question 20

how is human male made from sperm, egg

Answer 20

• sperm cell containing Y chromosome, fertilise ovum
• offspring possess 1 X 1Y chromosome
• male

Question 21

Define mutation.

Answer 21

random change, nucleotide sequence of gene, or number of chromosomes

Question 22

explain mutation causing Type 1 Diabetes Mellitus

Answer 22

1. mutation results, random change, nucleotide sequence, insulin gene
2. mutated gene, transcription, mRNA molecule, corresponding change, nucleotide sequence
3. mRNA undergoes translation, ribosomes, produce polypeptide, incorrect amino acid sequence, fold, dysfunctional insulin molecule
4. liver cells, dosent recognise dysfunctional insulin molecule,
5. does not absorb glucose or convert glucose -> glycogen,
6. even when excess glucose, bloodstream
7. excess glucose, excreted -> urine, Type 1 Diabetes Mellitus

Question 23

Down Syndrome cause, what characteristics

Answer 23

• change, chromosome number;
• Down Syndrome, trisomy chromosome 21.
• Stunted growth, mental impairment

Question 24

What are two factors that may increase the rate of mutation?

Answer 24

1. Ionising radiation
2. Chemical mutagens

Examples include X-ray and tar.

Question 25

What type of ionising radiation is mentioned as a factor increasing mutation rates?

Answer 25

Ultraviolet radiation ## Footnote Ultraviolet radiation is a form of ionising radiation.

Question 26

Name a chemical mutagen that may increase mutation rates.

Answer 26

Formaldehyde ## Footnote Formaldehyde is known for its mutagenic properties.

Question 27

What is the role of natural selection in evolution?

Answer 27

- mechanism, gradual change - **inheritable** characteristics - population - over time ## Footnote It involves the survival and reproduction of individuals with advantageous traits.

Question 28

Selection Pressure

Answer 28

1. Random gene mutation, sexual reproduction, genetic variation (**specific phenotype**) among (**individuals**), population 2. (**factor**) exerts, selection pressure, (**individuals**), (**advantaged phenotype**), better adapted, (**explain adaptation, environment**) 3. (**individuals**), (**disadvantaged phenotype**) dies **off**, (**factor**). 4. (**advantaged phenotype**) (**individuals**) **SURVIVE LONGER**, reproduce more offspring, **INHERIT** allele, (**advantaged phenotype**). 4. proportion, population, **ALLELE** (**advantaged phenotype**) increase gradually, many **GENERATIONS**, evolution, population, (**advantaged phenotype**). ## Footnote The specified phenotype can be any trait being studied.

Question 29

Define artificial selection.

Answer 29

The process whereby animal or plant breeders select organisms with desirable characteristics to reproduce. ## Footnote This results in the passing on of favorable alleles to offspring.

Question 30

Give an example of artificial selection.

Answer 30

Pollinate flowers belonging to soyabeans with high oil content with each other. ## Footnote This example shows how breeders can enhance specific traits in crops.

Question 31

Another example of artificial selection involves breeding cattle. What is the goal?

Answer 31

To produce large amounts of milk by breeding closely related individuals. ## Footnote This practice aims to enhance milk production traits in cattle.

Question 32

selection pressures evolution

Answer 32

1. overpopulation 2. changing environment 3. resource competition 4. predators

Question 33

continuous variation characteristics

Answer 33

1. intermediate forms, gradation, one extreme, another 2. affected by env. 3. controlled, many genes 4. show additive effect ## Footnote **additive effect** means (Gene 1 lower backbone height medium) + (Gene 2 higher backbone height tall) = relatively tall individual

Question 34

continuous variation example

Answer 34

height skin colour

Question 35

discontinuous variation

Answer 35

1. phenotypes distinct, one another, easily sorted, categories 2. not affected by env 3. controlled by 1, few genes 4. does not show additive effect