bio

What is DNA sequencing

The process of determining the precise order of nucleotide bases (A, T, C and G) in a DNA molecule or section of DNA.

What is genetic screening

Testing a person's DNA to identify specific genetic variants or mutations that may indicate an increased risk of a genetic condition or the possibility of passing it on to offspring.

What is DNA profiling

A technique in which individuals are identified/compared to others via their genetic markers

What is DNA barcoding

A method of identifying species based in the nucleotide (base) sequence of the genetic marker

What is a genome

The complete set of genetic material in an organism, including all of its DNA and all of its genes.

What is DNA

→ DNA (deoxyribonucleic acid) is the molecule that stores genetic information/instructions for an organism

What is a nucleotide

→ The basic building block of DNA

What is a chromosome

→ A long, tightly coiled package of DNA containing part or all of the genetic material of an organism

What is a gene

→ A section of DNA that contains the instructions for making a particular protein or functional product

What is an allele

→ An alternative version of a gene

How are DNA, genes and chromosomes related

→ DNA makes up chromosomes, and chromosomes contain many genes. A gene is a specific section of DNA

How does DNA become protein

→ DNA contains the instructions for making a protein. The base sequence is grouped into triplets, with each triplet coding for a specific amino acid. The amino acids are joined together in a polypeptide chain, which folds into a particular shape. The shape of the protein allows it to perform a particular function

What is mitosis

→ Mitosis is a type of cell division where one parent cell splits into two genetically identical daughter cells with the same number of chromosomes as the original cell

Why does mitosis occur

→ For growth, repair and replacement of damaged or old cells

What happens during mitosis and how many cells are produced

→ The cell's DNA is copied, the chromosomes are separated, and the cell divides to produce 2 genetically identical diploid cells

What is DNA replication and why does it occur

→ DNA replication is the process of copying DNA before cell division. It occurs so each new cell receives a complete copy of the genetic information

How does DNA replication occur

→ Helicase unwinds the parent DNA strand by breaking the hydrogen bonds between the complementary bases. Primase makes a primer, providing a starting point for DNA polymerase. DNA polymerase adds complementary nucleotides to build the new DNA strands. Ligase acts like glue, joining the DNA fragments together

What is semi-conservative DNA replication

→ Each new DNA molecule contains one half of the original strand still intact with the newly made strand, meaning half of the original DNA molecule is conserved

What are the main causes of genetic variation

→ Mutation, crossing over, independent assortment and random fertilisation

What is continuous variation

• Eg → Variation which can occur in a range of values. Height

What is discontinuous variation

Eg → Variation where individuals fall into distinct categories. ABO blood group

What is meiosis

→ Meiosis is a type of cell division where one diploid parent cell divides into four genetically different haploid gametes

Why does meiosis occur

→ To produce gametes (sex cells) for sexual reproduction

What happens during meiosis and how many cells are produced

→ The cell's DNA is copied, homologous chromosomes and then sister chromatids are separated, and the cell divides to produce 4 genetically different haploid cells with half the number of chromosomes as the original cell

What is crossing over

→ The exchange of sections of DNA between homologous chromosomes during meiosis

How does crossing over cause genetic variation

→ Homologous chromosomes line up next to each other, and neighbouring parts of the chromosome cross over, causing alleles to be exchanged. This creates chromosomes with new combinations of alleles. DNA gets shuffled, and each gamete produced has a different combination of alleles

What is independent assortment

→ The random arrangement and separation of homologous chromosome pairs during meiosis

How does independent assortment cause genetic variation

Homologous chromosome pairs separate randomly during meiosis, each gamete receives a different combination of material and parental chromosomes. This produces genetically different gametes and increases genetic variation

What is a mutation

→ A permanent change in the DNA base sequence

Why can mutations cause genetic variation

→ A mutation is a change in the DNA sequence of a gene that can create a new allele. This can change the instructions for making a protein, potentially producing a different version of the protein. Because the shape and function of a protein determine the characteristics it produces, this can result in a different trait, creating genetic variation

What is fertilisation

→ The fusion of two haploid gametes to form a diploid zygote

Why does fertilisation cause genetic variation

Any sperm can potentially fertilise any egg. Since each sperm and egg contains a different combination of alleles, random fertilisation creates a unique combination of alleles in the offspring, resulting in genetic variation

What is sexual reproduction

→ A biological process where two parent organisms combine their gametes to create a genetically unique offspring

What is asexual reproduction

→ A type of reproduction where offspring grow from a single parent without combining sex cells or gametes

Why does asexual reproduction produce little genetic variation

→ There is no meiosis or fusion of genetically different gametes, offspring generally receive the same genetic information as the parent

What is a genotype

→ The genetic makeup of an organism, referring to the alleles it has

What is a phenotype

→ The observable characteristics of an organism, influenced by its genotype and the environment

What is genetic variation

→ Differences in the genetic information between individuals of the same species

What is an adaptation

→ An inherited characteristic that increases an organism's ability to survive and reproduce in its environment

What is natural selection

→ The process where individuals with advantageous inherited characteristics are more likely to survive and reproduce, causing those characteristics to become more common over generations

What is gene flow

→ The movement of alleles between populations when individuals migrate and reproduce in another population

How can migration cause genetic variation

→ Migrating individuals introduce new alleles into a population, increasing genetic variation and changing the allele frequencies of the population

What are the 3 types of natural selection

→ Directional selection, stabilising selection and disruptive selection

What is directional selection

→ Selection that favours one extreme phenotype, causing the population's average phenotype to shift towards that extreme

What is stabilising selection

→ Selection that favours the intermediate phenotype and selects against the extreme phenotypes

What is disruptive selection

→ Selection that favours both extreme phenotypes and selects against the intermediate phenotype

What is a population bottleneck

→ A sudden reduction in population size that leaves a small group of survivors with a reduced and random sample of the original population's alleles

How does a population bottleneck affect genetic variation

→ It can reduce genetic variation because many alleles may be lost when the population is suddenly reduced

What is inbreeding

→ Reproduction between closely related individuals within a population

How can inbreeding affect genetic variation

→ It increases the chance of offspring inheriting the same alleles from both parents, reducing genetic variation within the population

What is the founder effect

→ When a small group of individuals becomes isolated from a larger population and starts a new population

How does the founder effect affect genetic variation

→ The new population has only a small, random sample of the original population's alleles, so some alleles may be lost and allele frequencies can be different

What is homozygous

Having two identical alleles for a gene, e.g. AA or aa.

What is heterozygous

Having two different alleles for a gene, e.g. Aa.

What is a dominant allele

An allele that is expressed in the phenotype when at least one copy is present, e.g. AA or Aa.

What is a recessive allele

An allele that is only expressed in the phenotype when two copies are present, e.g. aa.

Gene pool

Total collection of all alleles present in a population

Allele frequency

How common a particular allele is wuthub a population