3.1 & 3.2 GENES AND CHROMOSOMES Topic 3 & 10: Genetics.

3 .1 & 3 .2 GENES AND CHROMOSOMES

Topic 3 & 10: Genetics

READ & CONSIDER UNDERSTANDINGS3.1 .1 – 3 .1 .5

1 – Genes + Alleles

• What is a gene?• Based on the image above, what is an allele?

Gene

A gene is a heritable factor that influences are specific characteristic and occupies a particular locus.

All individuals of a species carry the same genes at the same loci on the same chromosome. How then is each individual unique?

Allele

Allele: one specific form of a gene, differing form other alleles by one or a few bases only and occupying the same gene locus as other alleles of that gene.

Mutation

Mutation – a change in the amount of chemical structure of DNA which results in the alteration or non-production of a protein and the mRNA that codes for it. Somatic mutation Germ line mutation

Gene Mutation

Gene mutations are changes in the sequence of bases in the DNA of a gene. They are extremely rare because the DNA polymerase has a built-in checking mechanism as it operates.

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READ & CONSIDER UNDERSTANDINGS3.2 .1 – 3 .2 .7 & 3 .2 .9 – 3 .2 .10

2 - Chromosomes

• How many chromosomes does a human cell have? Human egg or sperm?

Prokaryotic DNA

Prokaryotes have one circular chromosome that is replicated via binary fission.

Unique genetic characteristics arise from plasmids containing up to 12 genes. Eukaryote cells do not contain plasmids.

Eukaryotic DNA

Homologous Chromosomes

In eukaryotic species genes are carried on different chromosomes. Each parent contributes 23 chromosomes to the offspring, therefore supplying two different alleles of each gene present.

Chromosomes containing the same genes (though different alleles) are known as homologous hormones.

Diploid Nuclei Haploid Nuclei

Somatic cells are those found throughout the body containing a complete set of DNA (46 chromosomes in humans).

Gametes or sex cells contain one chromosome from each homologous pair. The selection is random allowing for high levels of genetic variation. A haploid nuclei contains 23 chromosomes.

Somatic Cell vs. Gamete

Karyogram

Review Cairns’ technique for

measuring chromosome length – page

102-103

Chromosome Mutation

Chromosome mutation may include a change in the number or sequence of genes. Additional chromosomes may occur (polyploidy) or there may be an alteration in part of the chromosome set.

#1 #2

Karyotype Analysis

#3 #4

Karyotype Analysis

#5 #6

Karyotype Analysis

#7 #8

Karyotype Analysis

#9 #10

Karyotype Analysis

READ & CONSIDER UNDERSTANDINGS3.1 .6 – 3 .1 .7 & 3 .2 .8

3 – Species Specifics

• What prevents interspecies reproduction?

Genome

Scientific Name Common Name Diploid Chromosome

s

# Base pairs

Homo Sapien Human 46 3200 x 106

Pan troglodytes Chimpanzee 48 --

Canis familiaris Dog 78 --

Oryza sativa Rice 24 --

Parascaris equorum

Roundworm 2 --

Escherichia coli Bacteria 1 4.6 x 106

Drosophila melanogaster

Fruit Fly 8 130 x 106

Paris japonica Canopy plant native to Japan

40 150000 x 106

The Human Genome Project

Works Cited

"Chromosomes." Genome BC Prenatal Case Study. N.p., n.d. Web. 11 Aug. 2015.

Kaebnik, Gregory E. "Synthetic Chromosomes." Center for Genetics and Society. N.p., 28 Mar. 2014. Web. 11 Aug. 2015.

Saltsman, Kristie. "Inside the Cell." Cellular Reproduction: Multiplication by Division:. National Institue of General Medical Sciences, 22 Apr. 2011. Web. 11 Aug. 2015.

Ticator, Statis. "Genetics and Regression Toward the Mean." The Statisticator. N.p., 9 Dec. 2012. Web. 11 Aug. 2015.