DNA, Cell Division, Genetics, Evolution, and Inheritance

These flashcards cover key concepts in DNA structure, replication, cell division, genetics, evolution, and inheritance.

DNA

A molecule that carries genetic information in all living organisms.

Structure of DNA

Double helix with two strands twisted together.

Nucleotides

Building blocks of DNA made of sugar, phosphate, and a base.

DNA Bases

A (adenine), T (thymine), C (cytosine), G (guanine).

Base pairing rules

A pairs with T, C pairs with G.

DNA replication

Copying DNA before cell division.

Importance of replication

So each new cell gets identical genetic information.

Key idea of replication

Semi-conservative; each new DNA = 1 old strand + 1 new strand.

Mitosis

Cell division producing 2 identical diploid cells.

Purpose of mitosis

Growth, repair, replacement.

Stages of mitosis

Prophase, Metaphase, Anaphase, Telophase.

Meiosis

Cell division producing 4 non-identical haploid gametes.

Importance of meiosis

Produces gametes and increases genetic variation.

Key processes in meiosis

Crossing over and independent assortment.

Gene

A section of DNA that codes for a trait.

Allele

Different versions of the same gene.

Genotype vs phenotype

Genotype = genetic makeup, phenotype = physical trait.

Monohybrid cross

A genetic cross involving one trait.

Punnett square

Predicts offspring genotypes and phenotypes.

Dominant vs recessive

Dominant = shows if present, recessive = needs two copies.

X-linked genes

Genes located on the X chromosome.

Why are males more affected by X-linked disorders?

They only have one X chromosome.

Pedigree

A diagram showing inheritance of a trait through generations.

Squares and circles in pedigrees

Square = male, circle = female.

Evolution

Change in species over time.

Gene pool

All alleles in a population.

Natural selection

Organisms with advantageous traits survive and reproduce.

Steps of natural selection

Variation → competition → survival → reproduction.

Speciation

Formation of new species.

Main cause of speciation

Isolation (geographical or reproductive).

Who proposed inheritance principles?

Gregor Mendel.

Mendel’s key idea

Traits are inherited as discrete units (genes).

Who discovered DNA structure?

Watson and Crick (with help from Rosalind Franklin).

Franklin's contribution

X-ray images showing DNA’s double helix shape.