Genes, Inheritance, and Selection (OCR)

Gamete

Gamete

These are reproductive cells, like sperm or egg cells, that carry half the genetic information (one set of chromosomes) an organism has.

Autosomes

Chromosomes that are not involved in determining sex.

Sex Chromosomes

Chromosomes that determine the sex of an individual.

Functions of Gene

1. Protein Coding

2. Non-coding RNA

Transcription

The process by which the information in a sequence of DNA nucleotides is copied to a newly synthesised messenger RNA (mRNA) strand.

Allele

One of two or more versions of a genetic sequence at a particular region on a chromosome.

Variant

Describes a subtype of a microorganism that is genetically distinct from a main strain, but not sufficiently different to be termed a distinct strain.

Complete Dominance

The dominant allele's phenotype completely masks the recessive allele's effect in heterozygous individuals.

Incomplete Dominance

The phenotype of heterozygous individuals is a blend of both alleles.

Dominant

An allele is dominant if it expresses its phenotype even when only one copy is present in the genotype.

Recessive

An allele is recessive if it expresses its phenotype only when two copies of the allele are present in the genotype.

Homozygous

An individual is homozygous for a trait if they have two identical alleles for that trait.

Heterozygous

An individual is heterozygous for a trait if they have two different alleles for that trait.

Genotype

The genetic makeup of an organism.

Phenotype

The observable characteristics of an organism, influenced by the genotype and environmental factors.

Genome

The complete set of DNA (deoxyribonucleic acid) in an organism, including all of its genes and non-coding sequences.

Human Genome Size

Approximately 3 billion base pairs.

Human Gene Count

About 20,000-25,000 genes.

Human Chromosomes Pairs

Humans have 23 pairs of chromosomes (46 total), including 22 pairs of autosomes (non sex-related chromosomes) and 1 pair of sex chromosomes (XX or XY).

Epigenetics

Study of changes in gene expression caused by mechanisms other than changes in the DNA sequence.

Discontinuous Variation

Traits with a limited number of distinct phenotypes.

Continuous Variation

Traits that exhibit a range of phenotypes.

Mutations

Changes in the DNA sequence that can occur spontaneously or due to environmental factors.

Point Mutations

Are single nucleotide changes.

Insertions/Deletions

Addition or loss of nucleotide segments.

Copy Number Variations

Duplications or deletions of large DNA segments.

Neutral Mutations

Most mutations have no effect on the phenotype.

Beneficial Mutations

Rare mutations that confer an advantage in the organism’s environment.

Harmful Mutations

Mutations that cause diseases or disorders.

Silent Mutations

Do not affect protein function and thus have no impact on phenotype.

Missense Mutations

Change one amino acid in a protein, which can alter its function.

Nonsense Mutations

Introduction of a premature stop codon leading to a truncated, usually nonfunctional protein.

Asexual Reproduction

The production of offspring by a single organism without the fusion of gametes.

Sexual Reproduction

The production of new organisms by the combination of genetic information of two individuals of different sexes.

Haploid

Cells containing a single (n) set of chromosomes.

Diploid

Cells containing two (2n) sets of chromosomes, one from each parent.

Punnett Squares

A tool used to predict the outcome of genetic crosses.

Monohybrid Cross

Involves one gene with two alleles.

Polygenic Inheritance

Traits that are controlled by multiple genes, each contributing to the phenotype.

Law of Segregation

Explains that each individual has two alleles for each gene, which segregate during gamete formation, so each gamete receives one allele.

Law of Independent Assortment

Explains that genes for different traits assort independently of one another during gamete formation.

Genetic Variation

Refers to the differences in DNA sequences between individuals of the same species.

Natural Classification Systems

Aims to group organisms based on their evolutionary relationships, reflecting their shared ancestry.

Microscopy

The invention of powerful microscopes allowed scientists to observe and categorize organisms based on cellular structures, leading to the identification of microorganisms and a deeper understanding of cell types.

Paleontology

The study of fossils provided insights into extinct organisms and their relationships to living species, refining the evolutionary picture.

Evolution

A change in the inherited characteristics of a population over time, through a process of natural selection, may result in the formation of new species.

Fossil Record

Fossils are the preserved remains or traces of organisms from past eras as they offer a glimpse into the history of life and provide a timeline for how life has changed over time.

Transitional Fossils

Fossils that exhibit characteristics of both ancestral and descendant species.

Fossil Distribution

The distribution of fossils across different geographic locations reflects the movement and diversification of life forms over time.

Antibiotic Resistance in Bacteria

Bacteria reproduce rapidly, and mutations in their DNA can occur during this process. Some mutations can provide bacteria with resistance to antibiotics, a phenomenon known as antibiotic resistance.

Antibiotic Use as a Selective Pressure

It is when antibiotics are used, they kill bacteria that are susceptible to them.

Increased Prevalence of Resistant Bacteria

Over time, the use of antibiotics selects resistant strains of bacteria, leading to an increase in their prevalence.

Vestigial Structures

When some organisms contain anatomical features that no longer have a purpose in the modern organism but may have had a function in an ancestral organism.

Molecular Evidence

Comparing DNA sequences from different organisms can provide evidence of evolution.

Voyage of the Beagle

A work by Charles Darwin where he observed distinct variations among species, particularly the finches on the Galapagos, which sparked his curiosity about the origin of these variations.

Independent Discovery

A work by Alfred Russel Wallace where he independently developed a similar theory of evolution by natural selection while working as a naturalists in Southeast Asia.

Seedbanks

Function like a safety net, safeguarding the genetic diversity of our planet's flora in the face of potential threats.