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BIOL 1090 Midterm: Nathan's midterm review

20 Pages

Course Code
BIOL 1090
Van Raayand Maathurs

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BIOL*1090 – Genetics Pwrpnt. 1 Summary 21:53 DNA and chromosome structure: - Ribonucleic acid (RNA) and Deoxyribonucleic acid (DNA) are polymers. Each subunit is a nucleotide comprised of: Phosphate group Five-carbon sugar or pentose Nitrogen-containg base 3 components together to make the four nucleotides of DNA A C T G - Purine and pyrimidine nucleotides are connected by phosphodiester bonds - DNA is double-stranded and the strands are antiparallel, they are held together by hydrogen bonds (2nm in width, 3.4nm middle length, bottom length is 0.34nm) - 5’ end has a free phosphate group - 3’ end has a free hydroxyl group - Opposing strands are said to be complementary ex – DNA sequence: 5’ AGTTCGT-3’ The compliment is 3’-TCAAGCA-5’ The reverse compliment is 5’-ACGAACT-3’ Most common form of DNA is B-DNA There are major and minor groove Formation of a chromosome: First Level: Packaging DNA into nucleosomes (produces 11nm fibre) Linker DNA – links the nucleosomes together, 2nm long Nucleosome core – 146 nucleotide pairs Linker region is likely to be digested by endonuclease DNA is wrapped around a nucleosome core of 8 histone proteins Nucleosome core contains 146 nucleotide pair while complete nucleosome contains 166 and contains histone H1 – both contain octamer of histones Second Level: Additional supercoiling of 11nm fibre to produce 30nm fibre  DNA in its most condensed form Third Level: Attachment of 30 nm fibre at many positions to a protein scaffold Cohesin – hold sister chromatids together after DNA synthesis Condensin – functions to condense the 30nm DNA fiber within on sister chromatid Telomere End of chromosome Resist degradation by DNases Prevent fusion of chromosomal ends Facilitate replication Centromere – middle of chromosome – provide the point of attachment of chromosomes to mictrobules in the mitotic spindle BIOL*1090 – Genetics Pwrpnt. 2 Summary 21:53 Cell Division Mitosis Each chromosome are comprised of two identical sister chromatids Cellular organelles are divided more or less between daughter cells But, nuclear chromosomes must be duplicated exactly and equally to daughter cells Main stages of the cell cycle: G1 Phase – growth, cellular metabolism S phase – DNA replication (chromosome duplication) G2 phase – preparation for mitosis M phase (mitosis) – chromosomal separate and cytokinesis Interphase – time between successive mitoses (G1+S+G2) Cells that are not actively cycling enter the G0. These are called quiescent BOTH CHROMATIDS ARE IDENTICAL CHROMATIDS Haploid (n) vs Diploid (2n) vs DNA content (c) N = # of unique genes C = weight of DNA Haploid – 1 chromatid BIOL*1090 – Genetics Pwrpnt. 2 Summary 21:53 Diploid – 2 chromatids together Interphase - Duplicate chromosomes called sister chromatids - Joined together by cohesin - Centrosome is duplicated Prophase - Initiation of spindle formation - Nucleolus disappears - Spindle microtubules invade Metaphase - Duplicated chromosome align midway between spindle poles - This equitoral plane is called the metaphase plate Nuclear membrane breaks down Anaphase - Chromosome move toward opposite spindle poles - Spindle poles move further apart Telophase - Chromosome cluster at opposite spindle poles - Chromosome disperse and decondense - Daughter cells form by cytokinesis BIOL*1090 – Genetics Pwrpnt. 2 Summary 21:53 - New daughter cells are 2n;2c BIOL*1090 – Genetics Pwrpnt. 3 Summary 21:53 Mitosis vs Meiosis Mitosis Occurs in stem cells End up with 2 diploid, genetically identical cells Meiosis Occur in germ (sex) cells End up with 4 haploid genetically distinct cells G1, S, G2 phase is the same BIOL*1090 – Genetics Pwrpnt. 3 Summary 21:53 Pachynema: Crossing over Breakage of chromatids and the exchange of broken pieces between homologous chromosomes (non-sister chromatids) Following cross over, homologous chromosomes start to pull apart, but remain joined at the cross over junctions (called chiasmata) Pairing of homolgous chromosomes is called synapsis and is often facilitated by formation of synaptonemal complex Spermatogenesis: BIOL*1090 – Genetics Pwrpnt. 3 Summary 21:53 BIOL*1090 – Genetics Pwrpnt. 3 Summary 21:53 Oogensis: BIOL*1090 – Genetics Pwrpnt. 3 Summary 21:53 BIOL*1090 – Genetics Pwrpnt. 3 Summary 21:53 BIOL*1090 – Genetics Pwrpnt. 4 Summary 21:53 Basic Principles of Mendelian Inheritance Locus: specific region on a chromosome Allele: Alternate form of a gene. Here we have two alleles: ‘A’ and ‘a’ The allelic combination is called the genotype The physical appearance is called the phenotype Homozygous: both alleles are identical (ll or aa or BB) Heterozygous
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