Biology - INHERITANCE, VARIATION AND EVOLUTION (B6)

DNA & the Genome -

What is DNA?

A polymer made of two strands forming a double helix, carrying genetic instructions.

DNA & the Genome -

What is a gene?

A small section of DNA that codes for a specific protein.

DNA & the Genome -

What is the genome?

The entire set of genetic material in an organism.

DNA & the Genome -

Why is understanding the human genome important?

Helps in identifying genes linked to diseases, understanding human evolution, developing personalised medicine.

Reproduction -

What are the two types of reproduction?

Asexual: One parent, no genetic variation

Sexual: Two parents, produces variation

Reproduction -

What happens in sexual reproduction?

Gametes (sperm + egg) fuse during fertilisation, combining genetic material.

Reproduction -

What is meiosis?

A type of cell division that produces four genetically different haploid gametes.

Reproduction -

Where does meiosis occur?

In the ovaries + testes to produce egg + sperm cells.

Reproduction -

How does meiosis differ from mitosis?

Meiosis produces gametes w/ half the chromosome number; mitosis produces identical cells for growth/repair.

Inheritance -

What is an allele?

Different versions of the same gene.

Inheritance -

What do dominant + recessive mean?

Dominant: Always expressed if present

Recessive: Only expresssed if two copies are present

Inheritance -

What is a genotype + a phenotype?

Genotype: The genetic makeup

Phenotype: The physical expression

Inheritance -

What does homozygous + heterozygous mean?

Homozygous: Both alleles are the same

Heterozygous: Two different alleles

Inheritance -

What is a Punnett square used for?

To predict the probability of inherited traits in offspring.

Inherited Disorders & Sex Determination -

Give two examples of inherited disorders.

Cystic fibrosis - caused by a recessive allele

Polydactyly - caused by a dominant allele

Inherited Disorders & Sex Determination -

What is embryo screening?

Testing embryos for genetic disorders before implantation / birth.

Inherited Disorders & Sex Determination -

What are some issues w/ embyro screening?

Ethical concerns (designer babies)

Expensive

May lead to discrimination

Inherited Disorders & Sex Determination -

How is sex determined in humans?

XX = female

XY = male

(Male gamete determines sex)

Variation & Evolution -

What causes variation in a species?

Genetic factors (inherited genes)

Environmental factors (e.g. diet)

A combination of both

Variation & Evolution -

What is evolution?

The gradual change in the characteristics of a population over time.

Variation & Evolution -

Who proposed the theory of evolution by natural selection?

Charles Darwin.

Variation & Evolution -

What is natural selection?

Organisms w/ advantages traits survive + reproduce, passing on those traits.

Variation & Evolution -

What is speciation?

The formation of a new species when populations become so different they can’t interbreed.

Selective Breeding & Genetic Engineering -

What is selective breeding?

Humans choosing organisms w/ desired traits to breed, to produce offspring w/ those traits.

Selective Breeding & Genetic Engineering -

Give two disadvantages of selective breeding.

Reduces genetic diversity

Increased risk of inherited diseases

Selective Breeding & Genetic Engineering -

What is genetic engineering?

Modifying the genome of an organism by inserting a gene from another organism.

Selective Breeding & Genetic Engineering -

Give one example of a genetically engineered organism.

Insulin-producing bacteria

GM crops w/ disease resistance / higher yields

Selective Breeding & Genetic Engineering -

What are some concerns about genetic engineering?

Unpredictable long-term effects

Ethical concerns

Potential impact on biodiversity

Fossils & Extinction -

How are fossils formed?

From hard parts not decayed

Impressions in rock

Replacement by minerals

In conditions preventing decay

Fossils & Extinction -

What can fossils tell us?

About how organisms have changed + evolved over time.

Fossils & Extinction -

Why is the fossil record incomplete?

Many organisms were soft-bodied

Conditions weren’t right for fossilation

Fossils may have been destroyed

Fossils & Extinction -

What can cause extinction?

New predators

New diseases

Environmental changes

Human activity