Transcript Chromosomes

Chapter 11
Meiosis and Sexual
Reproduction
Section 1
Reproduction
Chapter 11 Section 1:
Reproduction
Key Vocabulary
Terms
Adapted from Holt Biology 2008
Meiosis
A special process of cell division that results in
haploid sex cells
The total number of chromosomes decreases to
half the original number
Gamete
A reproductive cell; a haploid reproductive
cell that unites with another reproductive
cell to form a zygote;
Zygote
The cell that results from the
fusion of gametes (a fertilized egg)
Diploid
Describes a cell, nucleus, or organism that
contains two sets of chromosomes
Haploid
Describes a cell, nucleus, or organism that
has only one set of unpaired chromosomes
Homologous Chromosomes
Chromosomes that have the same order of
genes, the same structure, and that pair
during meiosis
Chapter 11 Section 1:
Reproduction
Supplementary Words
Adapted from Holt Biology 2008
Chapter 11
Section 1:
Reproduction
Notes
Adapted from Holt Biology 2008
Reproduction
Asexual
Reproduction - A
single parent
produces
genetically identical
offspring
Asexual Reproduction
Prokaryotes
Reproduce by
splitting - binary
fission
Asexual Reproduction
Unicellular
Eukaryotes
Reproduce by
mitosis and
cytokinesis
Asexual Reproduction
Multicellular
Eukaryotes
Reproduce by
Fragmentation – sea
stars
Budding – yeast, hydra
Cuttings - plants
Parthenogenesis –
water fleas, some bees
Advantages of Asexual
Reproduction
Many offspring are
produced in a short
mount of time.
Little energy is
required for Gamete
production
Finding a mate
Sexual Reproduction
Two parents
produce genetically
different offspring
Sexual Reproduction Background
Types of cells:
Germ cells – cells that
produce gametes
Somatic cells – other
body cells that do not
participate in sexual
reproduction
Advantages of Sexual
Reproduction
Genetically diverse
populations
Variety increases the
likelihood that some
individuals will
survive if the
environment changes.
Chromosome Number
Each chromosome
has thousands of
genes.
Chromosome Number
Each species has a
certain number of
chromosomes.
• Mosquitoes = 6
• Chimpanzees = 48
• Humans = 46
• Potato = 48
Human Chromosome Number
– Each somatic cell has two sets of 23
chromosomes.
– Each gamete has one set of 23
chromosomes.
• When fertilization occurs, the zygote will have two
sets of 23 chromosomes – one from each gamete.
23
23
+
46
=
Haploid and Diploid Cells
• Gametes are haploid
– Symbol: n
• Somatic cells are diploid
– Symbol: 2n
• For humans, n = 23 2n = 46
Homologous Chromosomes
• Paired chromosomes found in diploid
cells.
Autosomes and Sex Chromosomes
Autosomes
Chromosomes with
genes that do not
determine sex
Autosomes and Sex Chromosomes
Sex chromosomes
Chromosomes with
genes that determine
sex, X and Y in humans
–Boys have an X and a Y
–Girls have two Xs