Year 10 Human Biology Revision: DNA, Inheritance, and Mendelian Genetics

Flashcards covering DNA structure and replication, inheritance terms, mitosis and meiosis, mutations, and Mendelian genetics based on the Year 10 Human Biology revision guide.

DNA

Deoxyribonucleic acid.

Role of DNA

Determines the genetic characteristics of all living things.

Complementary base pairing

The specific pairing in DNA where Guanine pairs with Cytosine and Adenine pairs with Thymine.

Nucleotide

Smaller molecules that make up DNA, composed of a phosphate group, deoxyribose sugar, and one of four nitrogen rich bases.

James Watson and Francis Crick

The scientists who described the structure of DNA in 1953.

Double helix

The shape of DNA, described as a twisted rope ladder, with uprights made of alternating phosphate and sugar groups.

Chromosome

Thread like structures in the nucleus; composed of DNA and proteins; contains the genetic information in the form of genes.

Chromatid

One of the strands of a chromosome following replication.

Gene

A section of DNA that carries the genetic code for a particular characteristic.

Autosomes

All the chromosomes in a cell other than the sex chromosomes.

Sex chromosomes

The chromosomes that determine the sex of an individual; in humans they are the $X$ and $Y$ chromosomes.

DNA Helicase

The enzyme that causes strands of the double helix to separate from each other by zipping open to expose bases.

DNA polymerase

The enzyme that allows nucleotides to pair up with the exposed bases following the rules of complementary base pairing.

DNA Ligase

The stage or enzyme resulting in two identical DNA molecules, each a double helix identical to the original parent DNA.

Karyotype

An organised display of an individual’s chromosomes arranged into homologous pairs according to their size, shape and banding pattern.

Down Syndrome

An example of an abnormal karyotype also known as Trisomy 21.

Klinefelter Syndrome

An example of an abnormal karyotype characterized by the sex chromosomes $XXY$.

Mitosis

A process for the growth and repair of the body where a parent cell with 46 chromosomes produces two daughter cells, each with 46 chromosomes.

Meiosis

The cellular process that produces gametes (sex cells – eggs and sperm); results in 4 daughter cells each with 23 chromatids.

Fertilisation

The joining of eggs and sperm to produce new offspring.

Haploid number

The number of chromosomes in gametes, represented by $n$. In humans, this is $23$.

Diploid number

The number of chromosomes in body cells, represented by $2n$. In humans, this is $46$.

Asexual reproduction

Offspring are produced without any union of gametes, typically through mitosis.

Mutation

A mistake that happens as DNA is copied, causing a change to the base sequence.

Point Mutation

Mutations that usually affect one or a very few nucleotide base pairs, including deletion, insertion, or substitution.

Chromosomal mutation

Mutations affecting all or part of the chromosome structure or number, such as duplication, inversion, translocation, or removal of a whole chromosome.

Mutagens

Biological, physical, or chemical factors that increase the chance of a mutation, such as X rays, viruses, or benzene.

Non-disjunction

An error during cell division where chromosomes fail to separate at either Anaphase I or Anaphase II.

Interphase

The stage of mitosis where chromosomes replicate to have two chromatids.

Prophase

The stage of mitosis where replicated chromosomes and their chromatids become visible.

Metaphase

The stage of mitosis where replicated chromosomes line up along the equator of the cell.

Anaphase

The stage of mitosis where chromatids separate and move to opposite poles of the cell.

Telophase

The stage of mitosis where two nuclei form, each with the same number of chromosomes as the parent cell.

Cytokinesis

The final stage of mitosis where cell membranes form, making two daughter cells.

Homozygous

Having two identical alleles on homologous chromosomes, such as $AA$ or $aa$.

Heterozygous

Having two different alleles on homologous chromosomes, such as $Aa$.

Dominant

The trait that is observed in the outward appearance of a heterozygous individual.

Recessive

The trait that remains hidden in the heterozygous condition and is seen only in the homozygous condition.

Phenotype

Observable characteristics of the individual; the way the genotype is expressed.

Genotype

Genetic information carried by an individual.

Alleles

Different forms of the same gene located at the same point of homologous chromosomes.