Types of Cell Division Mitosis - Body cell replication Meiosis - Sex cell replication.
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Transcript of Types of Cell Division Mitosis - Body cell replication Meiosis - Sex cell replication.
Sexual reproduction:The production of offspring whose genetic
constitution is a mixture of that of two potentially genetically different gametes.
-Futuyma, p. 771
Sexual reproduction in diploid organisms:
-Chromosomes come in pairs
-One member of each pair comes from each parent
Sexual reproduction in diploid organisms:
-Chromosomes come in pairs
-One member of each pair comes from each parent
- Cells that will turn into gametes are sequestered early in development - minimizing replication.
Sexual reproduction in diploid organisms:
-Chromosomes come in pairs
-One member of each pair comes from each parent
- Cells that will turn into gametes are sequestered early in development - minimizing replication.
-At sexual maturity, gamete production begins.
Sexual reproduction in diploid organisms:
-Chromosomes come in pairs
-One member of each pair comes from each parent
- Cells that will turn into gametes are sequestered early in development - minimizing replication.
-At sexual maturity, gamete production begins.
-Gametes are haploid. Their union produces a new diploid organism.
Sexual reproduction in diploid organisms:
-Chromosomes come in pairs
-One member of each pair comes from each parent
- Cells that will turn into gametes are sequestered early in development - minimizing replication.
-At sexual maturity, gamete production begins.
-Gametes are haploid. Their union produces a new diploid organism.
-Non-chromosomal cell matter comes from the mother.
Meiosis
Sex cell division, aka gametogenesis
During meiosis, chromosome pairs double, then the
center two chromatids recombine, or
“cross-over”
Meiosis - Sex cell division, aka gametogenesis
3 chromosomes = 64 combinations but
only 1 to 4 gametes
Sampling error
Mutation-An error in replication of a nucleotide sequence, or any other alteration of the genome that is not manifested as reciprocal recombination.
Mutation is the ultimate source of all hereditary
variation
Basic types of mutations-
Point mutation
Insertion/Duplication
Deletion
Translocation
Inversion
Fis
Horizontal transfer
/Fusionsion
G
Point mutation -An error in replication of a nucleotide sequence.
For example, a daughter cell might end up
with a guanine molecule
where the parent cell
had a adenine molecule at
that same position in its
DNA sequence.
G
Point mutation -An error in replication of a nucleotide sequence.
For example, a daughter cell might end up
with a guanine molecule
where the parent cell
had a adenine molecule at
that same position in its
DNA sequence.
Many point mutations have no effect whatsoever on phenotype. This is very often the case when the mutation occurs in the third position of a nucleotide triplet
G
Point mutation -An error in replication of a nucleotide sequence.
Why would the position matter?
Many point mutations have no effect whatsoever on phenotype. This is very often the case when the mutation occurs in the third position of a nucleotide triplet
G
Point mutation -An error in replication of a nucleotide sequence.
Why would the position matter?
Because the DNA code is redundant.
Many point mutations have no effect whatsoever on phenotype. This is very often the case when the mutation occurs in the third position of a nucleotide triplet
G
Point mutation -An error in replication of a nucleotide sequence.
Why would the position matter?
Because the DNA code is redundant.
Many point mutations have no effect whatsoever on phenotype. This is very often the case when the mutation occurs in the third position of a nucleotide triplet
DNA nucleotide
triplets code for amino
acids.
G
Point mutation -An error in replication of a nucleotide sequence.
Why would the position matter?
Because the DNA code is redundant.
But there are 64 possible triplet combinations (“codons”) yet only 20 amino acids. DNA
nucleotide triplets code
for amino acids.
G
Point mutation -An error in replication of a nucleotide sequence.
Why would the position matter?
Because the DNA code is redundant.
But there are 64 possible triplet combinations (“codons”) yet only 20 amino acids.
Some combinations are synonymous.
DNA nucleotide
triplets code for amino
acids.
G
Point mutation -An error in replication of a nucleotide sequence.
For exampleBut there are 64 possible triplet combinations (“codons”) yet only 20 amino acids.
Some combinations are synonymous.
CCC codes for the
amino acid proline.
But so do CCA, CCT, and CCG
fmi see Futuyma,
p. 45
Insertions & Deletions
During meiosis, chromosome pairs double, then the
center two chromatids recombine, or
“cross-over”
Insertions & Deletions
Sometimes, the recombination is not perfectly reciprocal, producing “unequal
crossing-over”
InsertionDeletion
Translocation
Sometimes, chromosomal material is exchanged among
non-homologous chromosomes. Also, copies of certain nucleotide sequences can be transposed --inserted
on other chromosomes. Transposition events
sometimes occur in plants, eg flax, during times of
ecological stress. It is a quick way to disrupt the
phenotype, giving rise to new morphologies and
physiologies in one generation, thus allowing
rapid evolution of new adaptations.
Duplication
Deletion
Translocation
Equal crossing over
or
Equal crossing over
with
Unequal
crossing
over
Inversion
Sometimes, a bit of chromosomal material is
excised during recombination and ends up back in place, but upside
down.
Doublets Game post from Carl Zimmer’s blog: www.corante.com/loom/
The challenge of a doublet is to turn one word into another. You are allowed to change one letter at a time, but each change must produce a real word. Here's a doublet that suits a post on evolution: Change APE to MAN.
APEAPTOPTOATMATMAN
Doublets Game post from Carl Zimmer’s blog: www.corante.com/loom
Now imagine that having solved the APE-to-MAN puzzle, you tell a friend about your triumph. Your friend scoffs. "That's ridiculous," he says. "I don't believe you've found a missing link between APE and MAN. It doesn't exist."You furrow your brow. "Wait," you say. "No, I think maybe you didn't hear how the puzzle works--""I mean, what comes in between?""Well, there's APT, and then--.""APT? Please! That's nothing like MAN. They don't have a single letter in common. It's just a completely separate word on its own.""But then there's OPT--""OPT? Are you kidding me? That's just as irrelevant. You can't just go from APE to MAN through OPT.""But what about MAT? That's a lot like MAN.""Sure," your friend says, rolling his eyes. "But what on Earth does it have to do with APE?"
Doublets Game
MAN RAN RAM RIM RIB ROB
> translocation adds MAN
ROB MAN
> deletion takes away the B & the space
ROMAN
WOMAN
Structure of the genome
-integrated system of modules of various kinds
-10,000-100,000 genes in most metazoans
Structure of the genome
-integrated system of modules of various kinds
-10,000-100,000 genes in most metazoans
-90% or more is non-genic & “junk DNA”
Structure of the genome
-integrated system of modules of various kinds
-10,000-100,000 genes in most metazoans
-90% or more is non-genic & “junk DNA”
-repetitive sequence
Structure of the genome
-integrated system of modules of various kinds
-10,000-100,000 genes in most metazoans
-90% or more is non-genic & “junk DNA”
-repetitive sequence
-highly repetitive satellite DNA
eg. alu repeats have been inserted all over the genome of Drosophila
Structure of the genome
-integrated system of modules of various kinds
-10,000-100,000 genes in most metazoans
-90% or more is non-genic & “junk DNA”
-repetitive sequence
-highly repetitive satellite DNA
eg. alu repeats have been inserted all over the genome of Drosophila
-introns
DNA that codes for protein is arranged within the gene in a series of exons. The non-coding introns are spliced out during transcription and translation.
A gene generally forms part of a gene family, a group of genes descended from an ancestral gene.
Gene families evolve primarily via insertions.
When a second copy of a functional gene is inserted downstream (or sometimes on another chromosome), the second copy (and often the
original as well) is free to accumulate additional mutations without compromising
gene product volume or quality.
Gene families often have numerous member genes which specialise in producing subtly
different forms of the gene product at different stages of organismal development (eg. fetal
hemoglobin)
Locus 1 2 3 4 5
Alleles (versions)
equals
any Combination
Complex additive loci model
-Most traits arise from many genes working together
Complex additive loci model
-Most traits arise from many genes working together
Locus 1 2 3 4 5
Alleles (versions)
nearly black skin
Locus 1 2 3 4 5
Alleles (versions)
nearly translucent skin
Virtually no one would have all 10 of the same allele
Locus 1 2 3 4 5
Alleles (versions)
So these two very different
gene combinations both produce
the same skin tone, but share no alleles
So, in our hypothetical example:So, in our hypothetical example: