1. Cells and Heredity
Chapter 4

2. Bell Work 9/30/10
Answer #10-15 on page 95.

3. 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. 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.

5. 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 present in the genotype

6. Living things inherit traits in patterns.
alleles
a gene
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
Try a virtual version of Mendel’s experiment.
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7. Bell Work 10/1/10 Please use complete sentences
What is the difference between a genotype and a phenotype?
Explain why a person with an allele for a particular trait may not have a phenotype that shows the trait.

8. 4.2 Notes
Punnett square – illustrates how the parents’ alleles might combine in offspring (ratio, percentage) B b
B = black fur
b = brown fur BB Bb bb

9. Homozygous – both traits are the same (both dominant or both recessive)
Heterozygous – traits are different (one dominant one recessive)

10. Bell Work 10/4/10
Draw a punnett square for the following cross then write down the phenoype and genotype ratios and percentages.
Y = yellow flower y = white flower
A heterozygous yellow flower is crossed with a homozygous white flower.

11. Read page 116 and answer #1-3 at the bottom (not the example)
Bell Work 10/5/10
Read page 116 and answer #1-3 at the bottom (not the example)

12. 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

13. Bell Work 10/6/10
Write each sentence, then decide if these statements are true. If not true, correct them.
Mitosis produces four genetically identical daughter cells.
In sexual reproduction, offspring inherit traits from both parents.
Genetic traits are inherited in random patterns.

14. Meiosis Takes place in the reproductive tissues of an organism
A single cell goes through two cell divisions (meiosis I and meiosis II)

15. Meiosis I
Step 1 - Prophase I
Chromosomes condense
Duplicated chromosomes pair up with their partners
The nuclear membrane disappears

16. Meiosis I
Step 2 - Metaphase I
Chromosome pairs line up in the middle of the cell

17. Meiosis I
Step 3 - Anaphase I
Chromosome pairs separate and are pulled to opposite ends of the cell

18. Meiosis I
Step 4 - Telophase I and Cytokinesis
Nuclear membranes form
Cell divides into two daughter cells

19. Meiosis II
Step 1 - Prophase II
The nuclear membrane disappears

20. Meiosis II
Step 2 - Metaphase II
Chromosomes line up in the middle of the cell

21. Meiosis II
Step 3 - Anaphase II
Chromosomes separate forming individual chromosome and are pulled to opposite ends of the cell

22. Meiosis II
Step 4 - Telophase II and Cytokinesis
Nuclear membranes form
Both cells divide, producing four 1n cells

23. Bell Work
Please get a more punnett square practice sheet from by the sinks and begin working on it.

24. Answer number 7-16 on page 125 of the book.
Bell Work 10/8/10
Answer number 7-16 on page 125 of the book.
(bell work should be turned in today)

25. Meiosis is a special form of cell division.
4.3
Meiosis I 1n
Meiosis II
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