Transcript
Genetics Chapter 3:
- Bacterial Cell:
Lacks Nucleus
Has circular chromosome (not protected) found in the “Nucleoid Region”
One copy of each gene found in chromosome
Has a cell wall, inner plasma membrane, and free ribosome’s
Reproduction of Prokaryotes: Binary Fission
Asexual reproduction (copy chromosomes and creates two (2) identical daughter cell)
1) Elongates 2) separates 3) creates identical clones
Only form of variation is through Mutation
Prokaryotes
Eukaryotes
Circular chromosome
Linear chromosome
1 chromosome
Many chromosomes
No nucleus (nucleoid region)
Nucleus present
-Eukaryotes:
27527254381500 - has protected genetic c material & each chromosome has a gene
Diploid 2n = 6
N= 3
10763254495800Haploid (n)
Physical location of a gene on an chromosome is called its LOCUS
- AA = Same gene & same alleles (homozygous dominant)
- Bb = Same gene & diff alleles (heterozygous)
-cc = Same gene & same alleles (homozygous recessive)
N = 3
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*Chromosomes are HOMOLGOUS = genes are found in the same order
- Each chromosome is inherited from each parent (explains why can be homologous, same location of the genes but different alleles are present)
MITOSIS: cell cycle: cell getting rady for DIVISON
Skin cells, intestinal cells, blood cells (undergoes division)
G0 Phase: “Resting” Cell (2n = 6)
G1 Phase: Cell prepares for division
S Phase: Synthesis of DNA (Chromosomes replicate) (2n=6) HOWEVER, 12 chromatids presentrighttop
G2 Phase:
M Phase (Mitosis): Prophase, prometaphase, metaphase, anaphase, telophase (some undergo cytokinesis)
1 Chromosome –
Held together at the Centromere/ Kinetochore (proteins attached to centromere)
Centromere/Kinetochore: required for proper segregation during mitosis/meiosis
2 sister chromatids – Identical to one another
*Chromosomes do NOT condense during the S phase, but only once prophase starts
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Prophase: Chromosomes become ORGANIZED
Chromosomes condense
Nuclear envelope looses shape
Centrosomes separate to opposite side of the cell
Mitotic spindle forms
38195256429375Prometaphase:
Spindle fibers interact with:
Sister chromatids – pulls chromatids apart
Each other: push spindle poles apart (once
Stop pulling metaphase plate forms)
Spindle microtubles bind to kinetochores
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Metaphase: the METAPHASE PLATE forms as the spindle poles stop pulling as there is an equal pull in each direction
-114300-361950Anaphase: SEPERATION phase
connection holding sister chromatids break
-Each chromatid is pulled to separate poles (linked to only one pole)
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Telophase:
Chromosomes decondense
Summary of Mitosis:
Start: 1 parent cell (2n = 4)
Chromosomes replicate, condense, metaphase plate, pulled apart
End: 2 daughter cells (2n = 4)
Meiosis: (produces gametes)
2 successive divisions
Reduce # of chromosomes by ½
2n = 46 n = 23
50196754772025** Sex = genetic RECOMBINATION = genetic variation
Prophase I:
Chromosomes condense
Btwn 2 homologous chromosomes SYNATONEMAL COMPLEX forms
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DNA exchanges CROSSING OVER
43243506057900Structure formed is a CHIASMA
Synatonemal complex goes away & nuclear membrane fragments
Prometaphase I:
Each spindle grabs a pair of chromosomes
BIVALENT (tetrad) : 2 chromosomes lined up together
47910757943850Metaphase I:
Chromosomes lines up in the center (creates the metaphase plate)
Bivalents are organized along the metaphase plate (one chromosome linked to one pole, and the homologous chromosome linked to the other pole)
4324350390525Anaphase I:
Separates homologues (2 sister chromatids present)
47148752028825Telophase & Cytokinesis:
Cleavage Furrow forms & chromosomes reach their designated ‘poles’
Separates into two different cells (diploid)
Meiosis II: undergoes Mitosis but labeled Prophase II, etc
Summary of Meiosis:
Meiosis I synatonemal complex, crossing over, chiasma forms, tetrad, creates 2 diploid cells
Meiosis II creates 4 haploid cells
**Triploid or odd numbered organisms (3n, 5n, etc) can’t undergo meiosis because homologue chromosomes can’t pair up leads to sterile and INFERTILE organisms**
