Cells and Cells and HeredityHeredity

Chapter 4Chapter 4

Bell Work 9/30/10Bell Work 9/30/10

Answer #10-15 on Answer #10-15 on page 95.page 95.

4.1 Vocab4.1 Vocab

Sexual reproduction – a cell Sexual reproduction – a cell containing genetic information containing genetic information from the mother and a cell from the mother and a cell containing genetic information containing genetic information from the father combine into a from the father combine into a completely new cell, which completely new cell, which becomes the offspring.becomes the offspring.

4.1 Vocab Cont.4.1 Vocab Cont.

Gene – the basic unit of heredity Gene – the basic unit of heredity that consists of a segment of that consists of a segment of DNA on a chromosomeDNA on a chromosome

Heredity – the passing of genes Heredity – the passing of genes from parents to offspringfrom parents to offspring

Alleles – various forms of a gene. Alleles – various forms of a gene. Can be dominant or recessive.Can be dominant or recessive.

Genotype – genes an organism Genotype – genes an organism has.has.

Phenotype – the actual Phenotype – the actual characteristics that can be characteristics that can be observedobserved

Dominant allele – can be observed Dominant allele – can be observed in the phenotype even if only one in the phenotype even if only one copy is present in the genotypecopy is present in the genotype

Recessive allele – only observed in Recessive allele – only observed in the phenotype if two copies are the phenotype if two copies are present in the genotypepresent in the genotype

SECTION OUTLINESECTION OUTLINE

Living things inherit traits in Living things inherit traits in patterns.patterns.

Offspring inherit alleles, which are forms of genes, from their parents. Alleles come on chromosome pairs and can be dominant orrecessive. 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.

CLASSZONE.COMCHAPTERRESOURCESCHAPTERRESOURCES

alleles

a gene

Bell Work 10/1/10Bell Work 10/1/10Please use complete Please use complete

sentencessentences1.1. What is the difference What is the difference

between a genotype and a between a genotype and a phenotype?phenotype?

2.2. Explain why a person with an Explain why a person with an allele for a particular trait allele for a particular trait may not have a phenotype may not have a phenotype that shows the trait.that shows the trait.

4.2 Notes4.2 NotesPunnett square – illustrates how the Punnett square – illustrates how the

parents’ alleles might combine in parents’ alleles might combine in offspring (ratio, percentage)offspring (ratio, percentage)

B b

B

b

BB Bb

Bb bb

B = black furb = brown fur

http://www.classzone.com/redirect_science/chm05_pg111_punnett.html

Homozygous – both traits are Homozygous – both traits are the same (both dominant or the same (both dominant or both recessive)both recessive)

Heterozygous – traits are Heterozygous – traits are different (one dominant one different (one dominant one recessive)recessive)

Bell Work 10/4/10Bell Work 10/4/10Draw a punnett square for the Draw a punnett square for the

following cross then write down the following cross then write down the phenoype and genotype ratios and phenoype and genotype ratios and percentages.percentages.

Y = yellow flowerY = yellow flower y = white flowery = white flower

A heterozygous yellow flower is A heterozygous yellow flower is crossed with a homozygous white crossed with a homozygous white flower.flower.

Bell Work 10/5/10Bell Work 10/5/10

Read page 116 Read page 116 and answer #1-3 and answer #1-3 at the bottom at the bottom (not the example)(not the example)

Vocab 4.3Vocab 4.3Gametes – cells that contain half the usual Gametes – cells that contain half the usual

number of chromosomes. (one chromosome number of chromosomes. (one chromosome from each pair) 1from each pair) 1n n cell or haploid cellscell or haploid cells

Egg – a gamete that forms in the Egg – a gamete that forms in the reproductive organs of a female. 1reproductive organs of a female. 1n n cell or cell or haploid cellshaploid cells

Sperm – a gamete that forms in the Sperm – a gamete that forms in the reproductive organs of a male. 1reproductive organs of a male. 1n n cell or cell or haploid cellshaploid cells

Fertilization – the process that takes place Fertilization – the process that takes place when a sperm and egg to form one new when a sperm and egg to form one new cell. 2cell. 2nn cell cell

Bell Work 10/6/10Bell Work 10/6/10

Write each sentence, then decide if Write each sentence, then decide if these statements are true. If not these statements are true. If not true, correct them.true, correct them.

1.1. Mitosis produces four genetically Mitosis produces four genetically identical daughter cells.identical daughter cells.

2.2. In sexual reproduction, offspring In sexual reproduction, offspring inherit traits from both parents.inherit traits from both parents.

3.3. Genetic traits are inherited in Genetic traits are inherited in random patterns.random patterns.

MeiosisMeiosis

Takes place in the Takes place in the reproductive tissues of an reproductive tissues of an organismorganism

A single cell goes through A single cell goes through two cell divisions (meiosis I two cell divisions (meiosis I and meiosis II)and meiosis II)

Meiosis IMeiosis I

Step 1 - Prophase IStep 1 - Prophase IChromosomes condenseChromosomes condenseDuplicated chromosomes Duplicated chromosomes

pair up with their partnerspair up with their partnersThe nuclear membrane The nuclear membrane

disappearsdisappears

Meiosis IMeiosis I

Step 2 - Metaphase IStep 2 - Metaphase IChromosome pairs line up Chromosome pairs line up

in the middle of the cellin the middle of the cell

Meiosis IMeiosis I

Step 3 - Anaphase IStep 3 - Anaphase IChromosome pairs Chromosome pairs

separate and are pulled to separate and are pulled to opposite ends of the cellopposite ends of the cell

Meiosis IMeiosis I

Step 4 - Telophase I and Step 4 - Telophase I and CytokinesisCytokinesis

Nuclear membranes formNuclear membranes formCell divides into two Cell divides into two

daughter cells daughter cells

Meiosis IIMeiosis II

Step 1 - Prophase IIStep 1 - Prophase IIThe nuclear membrane The nuclear membrane

disappearsdisappears

Meiosis IIMeiosis II

Step 2 - Metaphase IIStep 2 - Metaphase IIChromosomes line up in Chromosomes line up in

the middle of the cellthe middle of the cell

Meiosis IIMeiosis II

Step 3 - Anaphase IIStep 3 - Anaphase IIChromosomes separate Chromosomes separate

forming individual forming individual chromosome and are chromosome and are pulled to opposite ends of pulled to opposite ends of the cellthe cell

Meiosis IIMeiosis II

Step 4 - Telophase II and Step 4 - Telophase II and CytokinesisCytokinesis

Nuclear membranes formNuclear membranes formBoth cells divide, producing Both cells divide, producing

four 1four 1n n cellscells

Bell WorkBell Work

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

Bell Work 10/8/10Bell Work 10/8/10

Answer number 7-16 on Answer number 7-16 on page 125 of the book.page 125 of the book.

(bell work should be turned in (bell work should be turned in today)today)

4.34.3

SECTIONOUTLINESECTIONOUTLINE

Meiosis is a special form of Meiosis is a special form of cell division.cell division.

CHAPTERRESOURCESCHAPTERRESOURCES

Meiosis II

1n

1n

1n

1n

Meiosis I