Download Meiosis II

Cells and Heredity
Chapter 4
Bell Work 9/30/10
Answer #10-15 on page
95.
4.1 Vocab
Sexual reproduction – a cell containing
genetic information from the mother
and a cell containing genetic
information from the father combine
into a completely new cell, which
becomes the offspring.
4.1 Vocab Cont.
Gene – the basic unit of heredity that
consists of a segment of DNA on a
chromosome
Heredity – the passing of genes from
parents to offspring
Alleles – various forms of a gene. Can
be dominant or recessive.
Genotype – genes an organism has.
Phenotype – the actual characteristics
that can be observed
Dominant allele – can be observed in
the phenotype even if only one
copy is present in the genotype
Recessive allele – only observed in
the phenotype if two copies are
Living things inherit traits in patterns.
alleles
Offspring inherit alleles, which are
forms of genes, from their
parents. Alleles come on
chromosome pairs and can be
dominant or
recessive. The alleles you have
are your genotype; the observable
characteristics that come from
your genotype are your
phenotype.
SIMULATION
CLASSZONE.COM
Try a virtual version of
Mendel’s experiment.
a gene
CHAPTER
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Bell Work 10/1/10
Please use complete sentences
1.
What is the difference between
a genotype and a phenotype?
2.
Explain why a person with an
allele for a particular trait may
not have a phenotype that
shows the trait.
4.2 Notes
Punnett square – illustrates how the
parents’ alleles might combine in
offspring (ratio, percentage)
B = black fur
b = brown fur
B
b
BB
Bb
B
b
Bb
http://www.classzone.com/redirect_science/chm05_pg111_punnett.html
bb
Homozygous – both traits are the
same (both dominant or both
recessive)
Heterozygous – traits are
different (one dominant one
recessive)
Bell Work 10/7/09
Decide if these statements are true. If not true,
correct them.
1. Mitosis produces four genetically identical
daughter cells.
2. In sexual reproduction, offspring inherit traits
from both parents.
3. Genetic traits are inherited in random patterns.
Page 115 #1-6
1.
2.
3.
They show how the parents’ alleles may be
passed on to offspring
Ratios compare one number to another
number. A percentage is a ratio that compares
a number to 100.
Determine all the possible outcomes and
represent it as a percentage.
Vocab 4.3
Gametes – cells that contain half the usual
number of chromosomes. (one chromosome
from each pair) 1n cell or haploid cells
Egg – a gamete that forms in the reproductive
organs of a female. 1n cell or haploid cells
Sperm – a gamete that forms in the reproductive
organs of a male. 1n cell or haploid cells
Fertilization – the process that takes place when a
sperm and egg to form one new cell. 2n cell
Meiosis
 Takes
place in the reproductive tissues
of an organism
 A single cell goes through two cell
divisions (meiosis I and meiosis II)
Meiosis I
Step 1 - Prophase I
 Chromosomes condense
 Duplicated chromosomes pair up
with their partners
 The nuclear membrane disappears
Meiosis I
Step 2 - Metaphase I
 Chromosome pairs line up in the
middle of the cell
Meiosis I
Step 3 - Anaphase I
 Chromosome pairs separate and
are pulled to opposite ends of the
cell
Meiosis I
Step 4 - Telophase I and Cytokinesis
 Nuclear membranes form
 Cell divides into two daughter cells
Meiosis II
Step 1 - Prophase II
 The nuclear membrane disappears
Meiosis II
Step 2 - Metaphase II
 Chromosomes line up in the
middle of the cell
Meiosis II
Step 3 - Anaphase II
 Chromosomes separate forming
individual chromosome and are
pulled to opposite ends of the cell
Meiosis II
Step 4 - Telophase II and Cytokinesis
 Nuclear membranes form
 Both cells divide, producing four 1n
cells
Meiosis is a special form of cell
4.3 division.
Meiosis I
1n
Meiosis II
1n
1n
1n
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