DNA, Genes, Chromosomes, and Inheritance

Flashcards covering key vocabulary from lecture notes on DNA, genes, chromosomes, cell division, mutations, karyotypes, inheritance, and DNA manipulation.

Genetics

The study of heredity.

Heredity

The study of biological inheritance, or the passing down of biological traits.

Biological inheritance

The handing down of genes.

Genes

The blueprints of life, instructing cells to build proteins which determine how we look and function.

DNA (Deoxyribonucleic acid)

A very long double chain molecule that looks like a spiral ladder, also known as the double helix, made of repeating chemical units (nucleotides) that contain specific 'bases' which form the DNA code.

Nucleotides

Building blocks of DNA, each made of a phosphate group, a pentose sugar, and a nitrogenous base. The phosphate group and pentose sugar make up the backbone of DNA.

Genes

Sections of DNA that code for specific characteristics such as eye color.

Chromosomes

Large bundled lengths of DNA wrapped that contain many genes. Contain large sections that do not code for genes, this non-coding DNA is often used in DNA identification and species classification.

The 4 bases in DNA

Guanine, Cytosine, Adenine, Thymine

The Genetic Code

The order of bases in a single strand of DNA that instruct cells on which amino acids need to be joined together to make a particular protein.

Genetic code

A triplet or codon uses 3 bases to code for each individual amino acid.

Mitosis

This is when 1 body cell divides to make 2 identical copies of itself. Occurs every day and is needed for repair and growth.

Meiosis

When cells divide to form sex cells (sperm/egg cells). The copies made are not identical to the original cells.

Chromosomes in cell division

DNA as chromosomes must divide before cell division.

Mitosis

Duplicated chromosomes are pulled apart into different ends. The cell membrane the cleaves in the middle to form 2 identical daughter cells. Necessary for growth and repair.

Meiosis

A form of cell division used in sexual reproduction to ensure the next generation inherit copies of DNA from each parent. This cell division forms sperm and egg cells (gametes).

Changes in DNA

Errors can occur when the DNA code is replicated before mitosis. If not repaired, a mutation occurs, becoming a permanent change in the cell DNA sequence.

Mutagen

A factor that triggers mutations in cells.

Germline mutations

Mutations in germline cells that can be passed onto the next generations.

Somatic mutations

Mutations in body (somatic) cells that are not passed onto offspring.

Beneficial (positive) mutations

Variations that increase the chances of the organism surviving and reproducing, so therefore passing genetic information onto the next generation.

Deleterious (negative) mutations

May cause death of the organism or issues that prevent it from passing on genetic information to the next generation.

Neutral (no effect) mutations

Do not kill the organism or increase the chances of the genetics being passed on to the next generation, but these variations accumulate in the gene pool and lead to genetic variation in a population.

Point Mutations

Occur when there is a change to one of the nitrogenous bases (A, T, C, G). This could then in-turn change the order of the amino acids in a protein.

Substitution

Occurs when one nucleotide is swapped for another ( a change of base) -for example, ATG becomes ACG.

Insertion

Occurs when an extra nucleotide (or more than one) is inserted into the DNA sequence (for example, ATG becomes AT CG). Changes the DNA code for all amino acids that follow and is called a frameshift mutation.

Deletion

Occurs when a nucleotide is deleted from the sequence (for example, ATG becomes AG). Changes the DNA code for all amino acids that follow and is called a frameshift mutation.

Chromosomal Mutations

Affects multiple genes. As chromosomes occur as homologous pairs, if one chromosome is abnormal the other is still likely to be normal.

Duplication

Part of chromosome is copied, resulting in duplicate sections (potentially increases gene expression).

Inversion

A segment of a chromosome is removed and then replaced within the chromosome in reverse order.

Deletion

A portion of the chromosome is removed (along with any genes contained within this segment).

Insertion

A portion of one chromosome is removed and then replaced in a second chromosome.

Translocation

Segments of two chromosomes are exchanged (may interrupt gene sequences).

Genetic Engineering

Scientists can now transfer genetic material between species. These species are called Transgenic Organisms.

Genetically Modified Organisms

An organism which has had its genome altered by humans.

Gene Therapy

A copy of a functional gene is introduced into an organism. The gene is then switched on to produce the functional protein that is missing.

Karyotype

The complete set of chromosomes in an individual. It is grouped in pairs of homologous chromosomes and arranged by size.

Homologous chromosomes

A pair of chromosomes, one inherited from each parent.

Non-disjunction

A failure to separate homologous chromosomes during sperm and egg formation, resulting in one too many or one too few chromosomes in the gamete.

Trisomy

A medical term for having an extra copy of a chromosome.

Monosomy

The term for only having 1 copy of a chromosome.

Down Syndrome

Extra copy of chromosome 21, also called Trisomy 21.

Genotype

The genetic makeup of an organism, describing genes responsible for a trait or characteristic.

Phenotype

The appearance of an organism, or what it physically looks like, e.g. hair color, eye color etc.

Allele

One form of a gene that has 2 or more alternative forms.

Heterozygous

Genotype has two different alleles, e.g. Hh.

Homozygous

Genotype has two identical alleles, e.g. HH or hh.

Pedigrees

Charts that represent inheritance patterns in family trees. They indicate the phenotypes of individuals in successive generations within a family and are sometimes used to infer genotypes.

Restriction enzymes

Act like scissors and cut the double-stranded DNA molecule at a specific recognition site, resulting in hanging ends (sticky ends).

DNA ligase

Acts as a glue that rejoin the ends of DNA together.

Polymerase Chain Reaction (PCR)

This method is used to produce millions of copies of DNA from one piece using the complimentary base pairing rule (A-T & C-G).

Gel electrophoresis

A technique that is used to separate DNA fragments that have been cut into different sizes by restriction enzymes.