Year 10 Biology: DNA

Flashcards for Year 10 Biology DNA lecture notes.

Deoxyribonucleic acid (DNA)

A molecule that determines the genetic characteristics of most living things; it makes you who you are. Contains coded instructions that tell cells how to make proteins.

Nucleotides

Smaller molecules that make up DNA. They have three parts: a phosphate group, a deoxyribose sugar, and one of four nitrogen-rich bases.

Sugar-phosphate backbone

The backbone of a DNA strand, formed by nucleotides bonded together via the sugar and the phosphate group.

Nitrogenous bases

The bases that point inwards in DNA, forming a 'ladder' structure. There are 4 different nitrogenous bases: Adenine, Thymine, Cytosine, and Guanine.

Complementary binding

The way nitrogen bases bind together: Adenine only binds with thymine, and cytosine only binds with guanine.

DNA double helix

The twisted structure of DNA, like a twisted rope ladder, with sugar and phosphate molecules as the backbones and bases forming the rungs.

Gene

A section of DNA that contains the instructions for a specific protein.

Genetic code

The order of the nucleotide bases along the DNA strand, which codes for a specific protein.

Alleles

Different versions of genes; variations of genes that code for the same characteristic but have small changes in the way they are expressed.

Chromosomes

Long, thin, thread-like structures found in the nucleus of all cells, consisting of DNA wrapped around proteins. They are made of chromatin, which is DNA coiled tightly around proteins.

Somatic cells

Body cells that contain 46 chromosomes in humans.

Gametes

Eggs and sperm, which have only half as many chromosomes as body cells (23 chromosomes in humans).

Haploid nucleus

Nucleus has one chromosome of each type i.e. no homologous pairs. The cell contains 1 copy of every chromosome found in that species. A human haploid cell contains 23 chromosomes.

Diploid nuclei

Nuclei have 2 chromosomes of each type . The cell contains 2 copies of every chromosome found in that species. A human diploid cell contains 46 chromosomes.

Homologous chromosomes

Pairs of chromosomes that are similar in length, centromere position, shape, and contain the same genes (but may have different alleles). One is maternal, and one is paternal.

Autosomes

The 22 homologous pairs of chromosomes that code for all other genetic characteristics of the organism (not sex chromosomes).

Mutation

Changes to gene nucleotide sequences.

Mutagen

A factor that can increase the rates of mutations in cells (e.g., radiation, chemicals, carcinogens).

Replication

The process of copying DNA in the nucleus before a cell divides. Each DNA strand is copied exactly, creating 2 identical copies of the DNA double helix from the 1 original strand.

Sister chromatids

Identical copies of a chromosome; these are 2 identical strands of DNA joined by a centromere.

Mitosis

A form of cell division in eukaryotic cells that produces 2 genetically identical daughter cells.

Meiosis

A form of cell division in eukaryotic cells that produces gametes (egg and sperm) that have half the number of chromosomes than the parent cell.

Cell cycle

Cell cycle is the set of events that results in the creation of 2 daughter cells from 1 parent cell.

Interphase

The time between cell division.

Prophase

The first stage of mitosis.

Metaphase

Chromosomes align along the metaphase plate of the cell.

Anaphase

Sister chromatids break apart and move towards the poles of the cell.

Telophase

The final stage of mitosis, chromosomes un-condense to the state prior to prophase.

Cytokinesis

The dividing of the cell with the 2 nuclei into 2 separate cells with 1 nucleus each.

Crossing over

Crossing over: exchange of segments between non-sister chromatids of homologous chromosomes occurred during Meiosis; contributes to genetic variation.

Independent Assortment

During Metaphase I, each pair of homologous chromosomes orientates itself independently of all other pairs; contributes to genetic variation.

Fertilisation

In sexual reproduction, fertilisation results in the fusion of gametes to produce a zygote.