Science

Define variation

Variation is differences between individuals. There are two types — interspecific (within different species) and intraspecific (within individuals of the same species)

Define the term “species”

A group of organisms that can interbreed and produce fertile offspring, sharing common characteristics and genetic similarity.

What is the difference between eukaryotes and prokaryotes?

Eukaryotes are complex cells with a nucleus and organelles, while prokaryotes are simpler cells without a nucleus.

Why is variation important?

• Protection against disease, environmental change, introduced predators, etc

• Allows evolution to occur

• Survival of the fittest improves the species’ characteristics

What are the two types of intraspecific variation?

Aquired/non-inherited and inherited/herited

What is the base pairing rule?

Adenine — Thymine

Cytosine — Guanine

Describe the process of mitosis

1. In interphase, the DNA replicates. Each chromosome replicates to form two sister chromatids

2. Chromosomes line up on equator randomly

3. Chromosomes are pulled to opposite poles by spindle fibres

4. Fibres disappear. Nuclear membrane appears, chromosomes uncoil and are no longer visible

5. Two genetically identical daughter cells are produced

Define the term “crossing over”

In the very first stages of meiosis, homologus chromosomes line up their chromatids and the non-sister chromatids cross over to swap or exchange sections of DNA with each other and alleles get switched over. This means now different combinations of alleles are produced for the new daughter cells (gametes) thus beginning genetic variation

What is independent assortment

A random alignment and distribution of homologus chromosomes (both maternal and paternal) on the equator, ensuring each gamete contains a unique combination of genetic information

Define random segreagation

The process that occurs during meiosis where pairs of alleles are seperated and go into each cell when the homologus chromosomes split

A diploid cell…

has two complete sets of chromosomes

A haploid cell…

only has one set of chromosomes (half)

Describe the process of meiosis

Meiosis is the process of cell division for the production of gametes. It halves the chromosome number to produce four genetically unique daughter cells. Because of the processes that occur in different stages of meiosis (crossing over, independent assortment, and random segregation), every sex cell (gamete) in an organism has a different combination of alleles than any other sex cell.

Define the term “homologus pair”

A homologous pair is a pair of chromosomes (one from the mother and one from the father) that are the same size and shape, and carry the same genes in the same positions.

Define “mutation”

A permanent change in the base sequence of DNA during replication that leads to the creation of new alleles in the gene pool.

What is a mutagen?

Anything that causes or triggers a mutation (e.g cigarette carcinogen, radiation, UV light, some fatty foods, etc)

Define pure breeding

Pure breeding is when organisms are homozygous for the particular allele being studied and the parents with these particular alles produce offspring only with the same phenotype.

What is a test cross?

Breeding an unknown dominant phenotype with a known homozygous recessive individual to find the genotype of the unknown: if only offspring with a dominant phenotype are produced, the unknown is homozygous dominant. If any recessive phenotype offspring are produced, the unknown is heterozygous.

Define genetic biodiversity

The range of alleles present in a gene pool. Each species is the storehouse of an immense amount of genetic information in the form of traits, characteristics, etc

Define natural selection

The process in which environmental factors allow those organisms with favourable phenotypes/variations/adaptations to survive and reproduce

Define migration/gene flow

The movement of alleles between populations. There are two types:

• Immigration (genes introduced to gene pool)

• Emigration (genes lost from gene pool)

Define evolution and the four processes which can cause it

Evolution is the change in characteristics of a species over a gradual period of time. The four processes are:

• Natural selection

• Mutation

• Small population

• Migration

Why is it important that ecosystems are genetically diverse?

Genetic biodiversity is crucial for the long term survival, adaptation, survival, ecosystem functioning, resilience, and disease resistance of a species. Preserving genetic diversity is vital for the conservation and sustainability of our natural environments.

Low genetic diversity can make a population more vulnerable to diseases and environmental change, as it limits the possible adaptive responses.

What is the acronym for the importance of genetic biodiversity

LASERD

Long term survival

Adaptation

Survival

Ecosystem functioning

Resilience

Disease resistance

What is the process of natural selection?

• Individuals in a population show variation

• Individuals with less favourable characteristics within the population are killed due to selection pressures

• Over time, successful alleles become more common and an evolution of a new species occurs over a period of time

What are the three types of natural selection?

Stabilising selection, directional selection, and disruptive selection

Define stabilising selection

Selection pressures act against the two extremes of a trait, the median phenotypes are retained and become more common

Define directional selection

Selection pressure acts against one extreme of a trait, the population’s trait distribution shifts towards the other extreme

Define disruptive selection

Selection pressure acts against the median phenotype, resulting in the two extremes of a trait becoming more common

What is the bottle neck effect?

A sudden reduction of a large part of a population and their alleles due to a large scale natural or human induced event, leading to a decrease in genetic biodiversity and the gene pool

What is the founder effect

The loss of genetic variation that occurs when a new population is established from a larger population. This means the gene pool is smaller and there are less alleles within the new population

What is DNA sequencing

The process of identifying the exact order of bases in a strand on DNA. It is mainly done for genetic engineering, especially to study a specific gene/allele for mutation

What is genetic screening?

The process of sequencing a section of DNA to identify mutations in genes that can cause or increase the risk of a genetic disease

What is the purpose of genetic screening?

To test a population for a genetic disease in order to identify a subgroup of people that either have the disease or the ability to pass it onto their offspring.

What are some reasons for genetic screening?

• To learn if you have a genetic condition that runs in your family, before symptoms

• To learn if you could have a child with the condition

• To diagnose a genetic condition

  • To understand preventative treatment

What is DNA profiling?

Also called DNA fingerprinting, it is a technique in which individuals can be indentified and compared to others via their genetic markers. Mainly done in forensics for identifying criminals or fathers in paternity tests.

What is a genetic marker?

A gene or DNA sequence with a known location on a specific chromosome. Used to track a nearby unidentified gene.