Download Chromosome

10.1
Chromosomes
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Why are some cells smaller than others?
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What allow these cells to become
specialized into lung or muscle tissue?
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They have recently divided and have not
grown to full size.
Genes on chromosomes within each cell
contain the instructions for building those
specialized tissues.
How does each cell receive its genes?
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Mitosis. chromosomes are copied, divided
and received by daughter cells.
Developing embryo video
Karyotype
Male
Female
Down’s Syndrome
Formation of new cells
 2 trillion cells are produced by adults
each day.
 Cell division – cells grow and develop
depending on what they are dividing for:
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Healing wound
Asexual reproduction
 Gametes – organisms’ reproductive
cells, such sperm and eggs.
 DNA –
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must be present in each resulting cell.
Stores information on what proteins to
make and when.
Prokaryote cell reproduction
 Binary fission – is a form of asexual
reproduction that produces identical offspring.
 Process
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DNA is copied
Add new cell membrane between the two DNA.
Cell constricts
Cell wall forms around cell membrane
cell divides into two cells
Binary fission
Binary fission
Eukaryote cell reproduction
 Gene – segment of DNA that codes for a
protein or RNA molecule.
 Chromosome – the DNA and proteins
associated with DNA.
 Chromatide – two exact copies of DNA
that make up each chromosome.
 Centromere – the point two chromatids
are attached together.
Humans
 23 pairs of different chromosomes
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46 chromosomes
 Differ in size, shape and genes.
 Homologous chromosomes – are
chromosomes that are similar in size,
shape and genetic content.
 All cells are somatic cells, except gametes.
 Diploid – two sets of chromosomes.
 Haploid – one set of chromosomes.
 N = one set of chromosomes.
 Humans
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Haploid n=23
Diploid 2n=46
 Zygote – is a fertilized egg cell, the first cell of a
new individual.
Do not copy
Sex chromosomes
 Autosomes – chromosomes that are not
directly involved in determining the sex
(gender) of an individual.
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Humans 22 pairs
 Sex chromosomes – contains the
genes that will determine the sex of the
individual.
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Humans 1 pair (23)
Different sex traits (do not
copy)
 Many plants and some animals (earthworms
and hydra) have both male and female sex
organs in the same individual and produce both
male and female gametes (sperm and egg,
respectively).
 Among some dioecious taxa (some species of
fish, alligators and sea turtles) sex is
determined by the environment, not genetics.
Local concentrations of hormones or
differences in temperature will cause the
developing embryo to develop as either a male
or a female.
Change in chromosome
number
 It is essential to have all 46 chromosomes for
normal development and function.
 Trisomy – three copies of a particular
chromosome
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Trisomy 21 (Down’s syndrome) – extra copy of
chromosome 21.
 Karyotype – a photo of the chromosomes in a
dividing cell that shows the chromosomes
arranged by size.
karyotype
Change in chromosome
structure
 Mutations – change in chromosomes’
structure.
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Breakage of chromosome
mutation – a piece of the
chromosome breaks off completely.
 1.Deletion
2.Duplication mutation – a
chromosome fragment attaches to
its homologous chromosome.
3. Inversion mutation –
chromosome piece reattaches to
the original chromosome, but in
reverse orientation.
4. Translocation mutation – a piece
reattaches to nonhomologous
chromosome.