HEREDITY

Question 1

What are the key differences between sexual and asexual reproduction in terms of genetic variation and reproductive processes?

Answer 1

Sexual reproduction:
- Involves two parents and the production/fusion of male and female gametes.
- Requires meiotic division followed by mitotic division.
- Results in offspring with genetic variation, containing characteristics from both parents.
- Greater ability to adapt to changing environmental conditions.
Asexual reproduction:
- Involves only one parent and no production or fusion of gametes.
- Requires only mitotic division.
- Offspring are genetically identical to the parent (clones).
- less gene variation, reduced adaptability to environmental changes.

Question 2

What are the advantages and disadvantages of internal and external fertilisation?

Answer 2

Internal fertilisation:
- Occurs inside the female reproductive tract.
- Negatives:
- Fewer female gametes and many male gametes produced.
- Parental care is often provided for eggs or offspring.
- Positives:
- Higher chances of fertilisation
- Reduced risks from predators and environmental threats.
- Examples: mammals.
External fertilisation:
- Occurs outside the female reproductive tract, typically in water to prevent desiccation.
- Positives:
- Large numbers of both male and female gametes are produced.
- No parental care provided.
- Negatives:
- Lower chances of fertilisation.
- Offspring are often left vulnerable
- Examples: amphibians, fish.

Question 3

What are the advantages and disadvantages of asexual reproduction in plants?

Answer 3

Advantages:
- Rapid multiplication, allowing for quick growth and seed production to aid dispersal.
- Increased survival chances after extreme events (e.g., bushfires, cold) as no mating is required.
- Lower energy requirement for reproduction since only one parent is needed.
Disadvantages:
- Lack of genetic variation, making the population more vulnerable to diseases or environmental changes.
- Overcrowding and competition due to limited or no seed dispersal mechanisms.

Question 4

What are the key stages and processes involved in sexual reproduction in plants?

Answer 4

Pollination:
- The male part, stamen (anther and filament), produces pollen.
The female part, pistil (stigma, style, ovary), receives pollen on the stigma.
Pollen is transferred to the stigma by external agents like wind, water, animals.
- Cross-pollination increases genetic variation, while self-pollination ensures reproduction without external agents.
Fertilisation:
- Pollen travels down the style to fertilise the ovule inside the ovary, forming a zygote.
- The fertilised ovule becomes a seed containing the embryo.
Seed Dispersal:
- Seeds are dispersed by abiotic agents (e.g., wind, water) or biotic agents (e.g., animals).
-Dry fruits are usually dispersed by abiotic agents; fleshy fruits by biotic agents.
Germination:
- Seed germinates when conditions (water, oxygen, warmth) are suitable.
- The embryo grows into a young plant, eventually maturing to restart the reproductive cycle

Question 5

What are the different methods of reproduction in fungi, and how do they ensure the continuity of the species?

Answer 5

Budding:
- A small bud forms and detaches from the parent, creating a new individual.
Fast reproduction, no mate needed, but no genetic variation.
Asexual Spore Reproduction:
- Spores are produced and dispersed, growing into new fungi.
Rapid reproduction and wide colonisation, but offspring are genetically identical.
Sexual Spore Reproduction:
- Haploid hyphae fuse, creating genetically diverse spores.
Increases genetic variation, allowing adaptation to environmental pressures.

Question 6

What are the different methods of reproduction in bacteria and how do they ensure the continuity of the species?

Answer 6

Binary fission
- DNA is replicated.
- The cell elongates and divides via cytokinesis.
- Two genetically identical daughter cells are produced.
Ensures Continuity:
- Fast reproduction
- No mate required: time and energy, efficient.
Limitations:
- Lack of genetic diversity, but high mutation rates during DNA replication can introduce some variability.

Question 7

How has understanding plant and animal reproduction been applied in artificial reproduction to improve agricultural yields?

Answer 7

Method: Hand pollination by dusting pollen onto the stigma –> increases yield, boosts genetic variability.
- Labour-intensive, decreased genetic diversity with overuse.

Method: Collection, freezing, insertion of semen –> higher quality offspring, increased food production, conservation
Costly, long time, overuse–>reduce diversity .

Method: cuttings, bulbs, tubers, grafting –> produces clones with desirable traits (disease resistance)
- less genetic diversity, vulnerability to disease+selection pressures.

Question 8

What are all the steps for mitosis?

Answer 8

Interphase, prophase, metaphase, anaphase, telophase, cytokenesis

Question 9

What are the main functions of mitosis?

Answer 9

• increase body cells for growth
• replace ‘worn out’ cells
• repair damaged cells
• asexual reproduction

Question 10

What are all the steps for meiosis?

Answer 10

Early prophase, late prophase, metaphase I, anaphase I, telophase I, cytokenesis I, metaphase II, anaphase II, telophase II, cytokenesis II

Question 11

What are the main functions of meiosis?

Answer 11

• produces haploid sex cells with half the chromosome number of somatic cells.
• Increases genetic diversity through crossing over and independent assortment –> unique combinations of alleles.
• Maintains a stable chromosome number across generations when gametes fuse during fertilisation.

Question 12

What are the components of a DNA nucleotide?

Answer 12

deoxyribose sugar, phosphate, nitrogenous base

Question 13

What are nitrogenous bases held together by?

Answer 13

Weak hydrogen bonds which are easy to pull a part when replicating DNA.

Question 14

What are the components of a RNA nucleotide?

Answer 14

ribose sugar, phosphate, nucleotide

Question 15

how does mitosis effect continuity of species?

Answer 15

• growth+repair –> survival
• asexual reproduction

Question 16

how does meiosis effect continuity of species

Answer 16

• produces haploid sex cells with half the chromosome number of somatic cells.
• crossing over and independent assortment, resulting in unique combinations of alleles –> genetic diversity
• maintains a stable chromosome number across generations when gametes fuse during fertilisation

Question 17

how does DNA replication effect continuity of species

Answer 17

correct DNA replication –> correct proteins are made that are essential for survival

Question 18

characteristics of DNA in prokaryotes

Answer 18

• DNA in cytoplasm as lack a nucleus.
• single circular chromosome containing all genomic DNA.
• contain plasmids: small, circular extrachromosomal DNA segments carry additional genes.

Question 19

How is DNA organised in eukaryotic cells?

Answer 19

• Genomic DNA is stored within chromosomes inside the nucleus.
• Consists of multiple pairs of linear chromosomes, allowing greater genetic variation through sexual reproduction.

Question 20

What are the key steps for transcription?

Answer 20

1. RNA polymerase attaches itself to the promoter.
2. DNA unwinds –> separate only at the part of DNA that contains the gene to be used.
3. Non-coding strand of DNA –> complementary mRNA.
4. In eukaryotes, transcribed mRNA is called pre-mRNA. Pre-mRNA contains coding sequences of nucleotides called exons –> amino acids. Between these exons are sequences of nucleotides called introns –> mRNA is spliced
5. After splicing –> mature mRNA is formed –> mRNA moves from the nucleus to the cytoplasm for translation to occur.

Question 21

Where does transcription and translation occur?

Answer 21

Transcription occurs in the cytoplasm, translation occurs in ribosome

Question 22

What are the key steps for translation?

Answer 22

Ribosomes match tRNA anticodons with mRNA codons. tRNA carries specific amino acids, released upon pairing.
Amino acids join via peptide bonds to form a polypeptide chain.
Polypeptide chain folds or binds with others to form a functional protein.

Question 23

What is the role of mRNA in protein synthesis?

Answer 23

• single stranded RNA transcribed from a DNA template.
• carries codon triplets with instructions for amino acid assembly.
  mRNA is transcribed from DNA, carrying the gene’s instructions to the ribosome.
• ensures mRNA codons pair with tRNA anticodons, assembling amino acids in the correct sequence.
• forms a polypeptide chain that folds into a functional protein.

Question 24

What is the role of tRNA in protein synthesis?

Answer 24

• anticodon on one end and specific amino acid on the other.
• ensures each amino acid added to the polypeptide chain matches the mRNA codons during translation.
• carries only one type of amino acid, determined by its anticodon sequence.
• correct amino acid sequence allows proper protein folding
• errored sequence –> misfolded, non-functional proteins.

Question 25

What is the role of polypeptide synthesis in an organism?

Answer 25

• polypeptide chain –> functional protein
• organism function + development - each protein performs specific roles

Question 26

How do genes and the environment influence phenotypic expression?

Answer 26

• Genotype: genes determine trait
• Phenotype: Physical observable trait
  Gene Expression: Genes switched on/off –> produce proteins that determine phenotype.
• Incorrect gene sequences –> non-functional proteins.
• Nature vs. Nurture
• Environment modifies gene expression, affecting phenotype.

Question 27

function+eg of structural protein

Answer 27

• provides support
• collagen+elastin in skin

Question 28

function+eg of structural hormonal

Answer 28

• signalling proteins –> cell to communication –> coordinate activities in the body
• insulin regulates blood glucose level

Question 29

function+eg of structural enzymes

Answer 29

• catalyse metabolic reactions in the body
• amylase breaks down starch in the mouth and pancreas during
  digestion.

Question 30

function+eg of transport proteins

Answer 30

• carry substances around the body
• haemoglobin binds to oxygen and transports to cells through the
  blood

Question 31

function+eg of immunoproteins

Answer 31

• protects against disease causing organisms
• antibodies identify foreign materials in body for removal

Question 32

function+eg of immunoproteins

Answer 32

• voluntary and involuntary movement
• actin and myosin slide over one another –> muscle contraction.

Question 33

function+eg of storage proteins

Answer 33

• store mineral irons in the body
• ferritin –> regulates iron stored in body.

Question 34

how does meiosis contribute to genetic variation?

Answer 34

• crossing over - genes exchange between homologous chromosomes
• independent assortment -combinations of maternal and paternal chromosomes are aligned in metaphase
• random segregation - random separation of maternal and paternal
  chromosomes in anaphase

Question 35

How does fertilisation contribute to genetic variation?

Answer 35

• fusion of two gametes –> zygote with distinct allele combination.
• many possible gamete pairings –> gene combinations –> variation

Question 36

How do mutations contribute to genetic variation?

Answer 36

• change in the DNA sequence of a gene.
• creates new alleles with altered gene expression.
• if passed to offspring –> new allele in population.
• diversity to gene pool –> increased allele frequency and population variation.

Question 37

what’s co-dominance?

Answer 37

where both alleles inherited from homozygous parents are expressed in the heterozygous offspring

Question 38

what is incomplete dominance?

Answer 38

where the alleles of homozygous parents are expressed as a blend in the heterozygous offspring

Question 39

what are multiple alleles

Answer 39

when there is more than 2 possible alleles within in a population

Question 40

what type of trait is it if both parents aren’t affected but an offspring is affected?

Answer 40

autosomal recessive

Question 41

what type of trait is it if both parents are affected and an offspring is unaffected

Answer 41

autosomal dominant

Question 42

what type of trait is it if affected mother passes on the X-linked trait to the sons(s) but not to daughter(s)

Answer 42

sex-linked recessive

Question 43

What type of trait is it if:
a) Affected father passes on the X-linked trait to the daughter(s) but not to son(s).
b) Affected mother passes on the X-linked trait to both her daughter(s) and son(s).

Answer 43

sex-linked dominant

Question 44

what is a gene pool?

Answer 44

total of all the genes and their alleles within a population

Question 45

what is genetic diversity?

Answer 45

total of all the characteristics in the genetic makeup of a species

Question 46

what does the process of DNA sequencing?

Answer 46

1. DNA isolated and replicated.
2. DNA denatured using heat, separated into single strands (template, complementary strand)
3. a primer binds to the start of the template strand, helps DNA polymerase start replication process.
4. DNA polymerase uses single DNA strand build the complementary strand of DNA using nucleotides.
5. The complementary strand will continue until chain-terminating nucleotide is reached, which prevents any further nucleotides from attaching.
6. terminator molecules are labelled with a different fluorescent dye depends on nucleotide base at the end of the chain.
7. dye labelled DNA strands are electrophoresed and passed through a laser beam.

Question 47

what does the process of DNA profiling include?

Answer 47

DNA profile shown as series of bands sections in our non-coding DNA called STRs (short tandem repeats) - repeat many times, unique to each individual.
- The number of repeats in these non-coding regions of DNA varies –> different DNA profiles.
- close relation = similar DNA profiles determines inheritance patterns on a global level+family level for paternity testing/forensics.
- Its limitations involve contaminated and ‘planted’ evidence in crime scenes.

Question 48

how are population genetics used in conservation management?

Answer 48

• make informed decisions about protecting populations that are
  endangered/near extinction.
• Conservation genetics looks at how genes are inherited in a population to avoid extinction
• useful for scientists when determining current and future strategies for conservation and maintenance of biodiversity.

Question 49

how is population genetics used in disease and disorder inheritance?

Answer 49

Monogenic disease - mutation in a single gene in all cells
- Congenital disease → present at birth
- prediction of genetic susceptibility - traditionally been based on
family background and pedigree analysis.
- with genetic testing, the diagnosis of monogenic diseases and probability of inheritance in future offspring quick+accurate
- Genetic testing - presence of the SNPs that are unique to a disease
can be quickly and easily through DNA sequencing.
- Large-scale screening and DNA analysis –> early detection+improved treatment options - predict inheritance of a disease/disorder.
- generating data on occurrence of specific genetic conditions

Question 50

how are population genetics related to human evolution?

Answer 50

• our understanding of human evolution was based on fossil evidence - incomplete+subjective
• examining the genetic variation and similarity in modern day humans –> determine origin of civilisation + evolutionary pathway.
• evolutionary forces of mutation, natural selection, genetic drift, gene flow —> patterns of diversity in human populations today.
• number+frequency of alleles in a population are measures of diversity.

Question 51

what’s the multi-regional hypothesis and what does it suggest?

Answer 51

Multi-regional hypothesis (MRE) suggests that Homo sapiens evolved from ‘homo erectus’ outside of Africa.
- Homo erectus wandered out of Africa –> inhabited other regions –> evolved into modern humans.
- Modern genetic studies: if MRE were correct –> modern populations have ancient alleles over different regions of the world.

Question 52

what does the out-of-Africa hypothesis suggest?

Answer 52

• Modern humans (Homo sapiens) evolved in Africa 200,000 years ago~
• 60,000–80,000 years ago~ a group migrated out of Africa.
• Migrants spread across Europe, Asia, and other regions, replacing local hominins (e.g., Neanderthals).
• Supported by genetic, fossil, archaeological evidence.
• Higher genetic diversity in African populations –> all humans link to African ancestry.