Genetics & Evolution

Front 1

Define the term ‘genome’

Back 1

The ENTIRE DNA content of an organism, however only one copy is considered in the DNA.

On a smaller scale such as bacteria the genome is thechromosome(s)

Front 2

Describe the main components of eukaryotic genomes

Back 2

Eukaryoticgenomes are generally more complex dueto severaldifferent types of noncoding sequences.

The components of the nuclear genome are chromatin,which is the double – stranded helical structure of DNA

Front 3

Similarities of Nuclear and Organelle Genomes

Back 3

37 genes all involved in mtDNA

nDNA genes are also needed for functional mitochondria.

Sequences can vary widely in rates of evolution

Front 4

Differences of Nuclear and Organelle Genomes

Back 4

MtDNA is smaller in animals but large in nDNA

MtDNA Circularand single chromosome (haploid)

nDNA Multiplechromosomes, usually linear and in pairs (diploidy)

MtDNA Maternallyinherited while nDNA is biparental inheritance.

Recombination is absent in MtDNA but present in nDNA.

nDNA divisionby mitosis and meiosis, Includesrange of sequence types, including a lot of non-genetic sequence.

MtDNA mainly coding sequence

Front 5

Describe patterns in genome size in eukaryotes

Back 5

Genome size is measured as the amount of DNA in a haploidcell (onecopy of the genome).

Genome size is usually largerin eukaryotes than prokaryotes (usually >10^7bp)

Its also variable within eukaryotes

(~80 000-foldvariation) and can be quite large (up to 10^11 bp)

Front 6

Why the variation in Genome Size

Back 6

Genome size is correlated with organism complexity at somelevels.

With prokaryote genomes typically smaller and the minimum genome sizewithin major taxa tends to be higher the more complex the taxon.

However overall there is NO strong correspondence betweenorganism complexity and genome size

Lack ofcorrespondence known as C-valueparadox due to the different amounts of non-coding sequences in the genomes ofdifferent species

Front 7

What is the number of Genes in Selected Organisms?

Back 7

Thenumber or G-value is variable but generally higher in more complex organisms

This amount of variation is small compared to the amount ofvariation in organism complexity (complexity of gene regulatory network is moreimportant than number of genes in determining organism complexity)

Front 8

What is the mainType of Genes by Function in Humans

Back 8

Largest G-value

Transcription Factors

Nucleic Acid Enzymes

Receptors

UNKNOWN function

Front 9

What is the distribution of genes in eukaryotic genomes

Back 9

Typicallyuneven tend to occur in clusters

Front 10

Describe the main typesof DNA sequence found in eukaryotic genomes and their relativeabundances

Back 10

There is a diverse range of sequence types (different toprokaryotes)

Only a very small proportion of the genome is genic sequenceand only very small proportion of the remainder appears to be related to genefunction (usually)

refer to diagram pg. 6

Front 11

Discuss the genome evolution

Back 11

From an evolutionary perspective the genome is very dynamic(highly mutable)

Sequences change positions regularly and are duplicated anddeleted

Many of these changesare probably inert but not all

Front 12

Discuss the mechanisms of evolutionary novelty in eukaryotes (5)

Back 12

1. De novo

Wherea new gene evolves from non-coding sequence. RAREmost ‘new’ genes evolve from an existing coding sequence

2. Gene Duplication

Where a gene is duplicated and the duplicate evolves a new function (COMMON)

3. Exon Shuffling

Where 2> exons from different genes (or duplicated exonsfrom a single gene) combine About 19% of EUKARYOTIC genes have shuffled exons

4. Mobile Elements

Where a mobile element is integrated into agene and changes the gene function. WIDESPREAD

5. Gene Fusion

Two adjacent genes fuseinto a new gene Gene fission is alsopossible

Front 13

Mechanisms of Evolutionary Novelty

Back 13

1. Changes in Regulatory Genes

A changein a regulatory gene can potentially effect the expression of many genes

2. Gene Duplications

The most important mechanismsin the evolution of complex organisms

3. Chimeric Genes

New hybrid genes arising from gene fusion or exon shuffling

4. Whole Genome Duplications

5. Horizontal Gene Transfer

Transfer of genetic information from one organism toanother, separate from descent

High potential for evolutionary innovation

Front 14

Explain what a ‘chromosome’ is

Back 14

At a molecular level, a chromosome is DNA complex with histone and other proteins

(this complex is called chromatin)

Ata cellular level the details depend on the stage of the cell cycle

Front 15

Describe the process of mitosis.

Back 15

Mitosis is the basis of cellular inheritance in eukaryotes

It’s a type of nuclear division that produces two daughternuclei that are identical to the parent nucleus

The critical aspect is that the chromatids of singlechromosomes segregate to different poles (daughter nuclei)

Usual part of the growth or maintenance of populations ofcells

Front 16

Describe the process of meiosis

Back 16

Two successive nuclear divisions that give rise to haploidreproductive cells

The critical aspects of meiosis are that one member of eachhomologous pair segregates to different poles during the first division(meiosis 1) while the sisterchromatids of each chromosome separate to different poles during the seconddivision (meiosis 2)

n metazoans (animals) this occurs only in cells that giverise to reproductive cells (usually)

Front 17

Distinguishbetween somatic cell and germ cell mutations andtheirImplications

Back 17

Somatic cell mutations rarely affect survivorship, not heritable (exceptions are mutations cause cancer but still not heritable)

Germ cell mutations unlikely to affect survivorship, potentially heritable (exception if gamete containing mutation fertilised)

Front 18

Define the term 'chromosomalrearrangement'

Back 18

A chromosomal rearrangement is a type of mutation that isapparent at the level of the chromosome, typically involves large amounts ofDNA

Often one or more genes and therefore tends to havesignificant effects

The boundary between chromosomal rearrangements andDNA-level mutations is somewhat arbitrary (random) and shifting with improvedmethods for studying chromosomes

Front 19

Define each of the main types ofchromosomal rearrangements in eukaryotes

Back 19

Either changes in structure or number.

Structure is unbalanced or balanced.

Unbalanced is deletions or duplications.

Balanced is inversions and translocations.

Changes in numbers is aneuploidy or polyploidy.