Genetics and Evolution

Genes

The instructions for particular traits

What does DNA stand for?

deoxyribonucleic acid

Proteins

Chains of amino acids

Nitrogenous bases

adenine, guanine, cytosine, thymine

Complementary bases

A pairs with T and C pairs with G.

Nucleotides

Basic building blocks of DNA molecules, composed of a sugar, a phosphate, and a nitrogenous base.

Amino acids

building blocks of proteins; determined by the coding of a sequence of three bases

Homologous

Refers to matching pairs of chromosomes that carry the same genes

Non-homologous

refers to non-matching chromosomes that carry different genes

Mutation

permanent change in DNA sequence

Diploid

(2n) number of chromosomes in body cells

Haploid

(n) number of chromosomes in gametes - half the diploid number

Gametes

sex cells

Somatic cells

body cells

Number of chromosomes in humans

46 (23 pairs)

Mitosis

cell division in which the nucleus divides into two nuclei containing the same number of chromosomes.

Meiosis

cell division producing gametes with half the amount of chromosomes.

Steps of DNA replication

1. DNA unwinds

2. Daughter strands are formed using complementary base pairing

3. The DNA of the daughter strands wind together with its parent strand

Helicase

Unzips DNA

Which process of cell division results in genetically identical daughter cells?

mitosis

How many daughter cells are produced in meiosis?

4 haploid cells

How many daughter cells are produced in mitosis?

2 diploid cells

Phases of cell division

interphase, prophase, metaphase, anaphase, telophase

Which process has two rounds of cell division?

meiosis

Inheritance

the passing of DNA to offspring

Alleles

different versions of a gene (eg. brown eyes and blue eyes)

Dominant trait

A trait that is always expressed, even if the individual only has one copy of it (shown as a capital letter in genotypes)

Recessive trait

A trait that only shows if the individual has two copies of that allele (shown as a lower case letter)

Genotype

genetic makeup of an individual ie what alleles you have (eg. Bb)

Phenotype

appearance of the trait (eg. brown eyes)

Homozygous

identical alleles (eg. BB or bb)

Heterozygous

different alleles (eg. Bb)

Species

A group of similar organisms that can breed and produce fertile offspring.

Adaptations

inherited traits that improve an individual's ability to survive and reproduce

3 types of adaptations

structural, behavioral, physiological/functional

Natural selection

organisms better adapted to their environment are more likely to survive and produce more offspring, passing on the characteristics which helped them survive

Darwin's theory of evolution

1. variation always exists

2. some are better suited to the environment

3. only those who inherit the most fit traits will survive

4. these characteristics will be passed on to the next generations and increase in numbers

Speciation

the formation of new species by evolution

Process of speciation

1. isolation of a population

2. selection pressures lead to different adaptations

3. they become distinct species

Evidence for evolution

1. Fossil Record

2. Comparative anatomy

3. Comparative embryology

4. Chemical similarities (DNA)

5. Geographic distribution

Comparative anatomy: homologous structures

body part that is similar in structure on different organisms but performs different functions, suggesting a common ancestor (eg. forelimbs of humans, cats, bats and whales)

Comparative anatomy: analogous structures

look similar, same function, but different structure and development, no evolutionary relationship (eg. eagle and dragonfly)

Comparative anatomy: vestigial structures

Structures that were once utilized for some function or other but are no longer used in the same way (eg. wisdom teeth, appendix, tailbone)

Extinction

if a species fails to adapt, births < deaths and species stops existing entirely