Biology Exam Revision (Y10)

Cell Theory (Components)

1. All organisms are made of one or more cells.

2. Cells are the basic unit of structure

3. All cells come from other cells.

Prokaryotes (Open apartments)

Cells without a nucleus or membrane-bound organelles.

Eukaryotes (Mansions)

Cells with membrane-bound organelles (e.g. Golgi apparatus)

DNA Properties

1. It can make copies of itself

2. It carries the genetic information for protein-building

DNA Structure

1. Deoxyribose

2. Phosphate

3. One of four bases

Combination of a sugar, phosphate and base

Nucleotide

Types of DNA bases

Adenine, Thymine, Guanine, Cytosine

Complementary Base Pairing

Rules for which bases can connect with one another (A→T) (C→G)

Chromosomes

Tight package of DNA made of coiled histones into chromatin.

Circular Chromosomes

Plasmids

Difference of chromosomes versus chromatin

Chromosomes are only seen in cell division, chromatin is observed during interphase

Genes

Sections of DNA that code for a particular trait

Genetic variation

Differences in the genes to create separate, unique organisms

Smallest to Largest

Gene → DNA → Chromosome → Nucleus → Cell → (Multicellular) organism

Alleles

Variations of genes (Options)

Heredity

Genes that transfer from one generation to the next

Phenotype

The physical appearance based off a genotype and environmental factors.

Genotype

The combination of genes that determine a trait.

Wild-type phenotype

Most common phenotype in a population.

Mutant phenotype

Any phenotypes that are not the most common/wild-type.

How many chromosomes in a human cell?

46 chromosomes, 23 pairs

Types of chromosomes

1. Autosomes (22 pairs)

2. Allosomes (1 pair)

Mutations

Changes in the nucleotide sequence → Somatic cells or gametes. Harmful, neutral or beneficial.

Causes of mutations

Mutagens, UV radiation, Chemicals

Chromosomal mutations

Changes in the chromosomal structure (loss or gain of parts)

Gene mutations

Changes in the nucleotide/gene sequence. Can be one or several nucleotides.

Mitosis

Asexual reproduction and repair of cells/body.

Mitosis [PROCESS]

IPMAT

Meiosis

Creation of gametes and ensuring genetic variety (crossing over).

Meiosis [PROCESS]

IPMATPMAT

When does crossing over occur?

Prophase I

Nondisjunction

Too many/few chromosomes due to division errors.

Genome

All the DNA in an organism

Gene loci

Position of a gene on a chromosome

Heterozygous chromosomes

Both chromosomes have different alleles for a certain gene.

Homozygous chromosomes

Both chromosomes have the same allele for a certain gene.

Dominant trait

Only need one allele to be expressed → Stronger

Recessive trait

Need both alleles to be recessive to be expressed → Weaker

Law of Segregation

How genes are transmitted → Parents randomly provide one allele to a gamete

Codominance

Both alleles from a heterozygous individual are dominant and expressed. (WORKING TOGETHER). Parents are both homozygous dominant.

Incomplete dominance

The dominant allele is not fully expressed when with the recessive allele. (Red + White = Pink)

Natural Selection [REQUIREMENTS]

1. Variations (Phenotypic differences)

2. Heritability

3. Selection Pressure and Struggle

   1. Fitness

Phylogenetic tree

Shows evolutionary relationships of all species

Genetic biodiversity

Maximises survival of a species (Increasing the gene pool)

Species richness

Number of difference species in an area

Species abundance

Amount of a species in an area

Binomial Nomenclature [TAXONOMY]

KPCOFGS