im so tired a3.1 genetics

Variation

Differences among individuals (morphology

Genetic sources of variation

Mutation meiosis (crossing over and independent assortment) and fertilization

Environmental sources of variation

Nutrition temperature light and pH

Exam tip reasons for variation

Always state both genetic and environmental causes

Continuous variation

Controlled by polygenic inheritance and the environment often forms a bell curve e.g. height

Discontinuous variation

Distinct categories controlled by one or few genes e.g. ABO blood groups

Morphological Species Concept

Classifies species based on observable traits form and structure

Who developed binomial nomenclature

Linnaeus

Strengths of Morphological Species Concept

Simple and useful for fossils and field work

Limits of Morphological Species Concept

Can be misleading due to cryptic species or convergent evolution

Common mistake in species identification

Do not assume organisms that look alike are the same species

Biological Species Concept

Species are groups that interbreed in nature and produce fertile offspring reproductive isolation maintains boundaries

BSC works best for

Sexual species emphasizes shared gene pool

Why horses and donkeys are separate species

Their offspring mules are sterile

Rules for binomial names

Genus capitalized species lowercase italicized or underlined when handwritten

Abbreviating binomial names

After first use abbreviate genus e.g. E. coli

Benefits of binomial system

Universal avoids confusion and reflects relatedness

Exam tip species epithet

Do not capitalize species epithet or you lose marks

Chromosome number within species

Conserved diploid number 2n is even

Cause of chromosome number decrease

Fusion

Cause of chromosome number increase

Fission or polyploidy

Kingdom where polyploidy is common

Plants

Specifying chromosome number

Always state n or 2n

Human chromosome numbers

Somatic cells 2n equals 46 gametes n equals 23

Karyotype

Number size shape and banding pattern of chromosomes

Karyogram

Arranged image of chromosomes in metaphase by size centromere and banding sex chromosomes last

Chromosome centromere classifications

Metacentric submetacentric acrocentric telocentric

Centromere type not in humans

Telocentric

Chromosome arms

p arm short q arm long

Unity of genomes

Same genes and gene order allows homologous pairing in meiosis

Diversity of genomes

SNPs insertions and deletions

Human DNA similarity

Humans share 99.9 percent of DNA

Universal genetic code

All organisms use the same genetic code

DNA location in eukaryotes

Nucleus and organelles mitochondria and chloroplasts

C value paradox

Genome size does not correlate with gene number

C value

Haploid DNA content

Units for C value

Megabase pairs Mbp or picograms pg

pg to Mbp conversion

1 pg approximately equals 978 Mbp

Drivers of genome size differences

Polyploidy repeats transposable elements introns and duplications

Paramecium genome size

About 27 Mbp

Honeybee genome size

About 217 Mbp

Human genome size

About 3080 Mbp

Paris japonica genome size

About 150000 Mbp largest known plant genome