TYPES OF REPRODUCTION AND MEIOSIS

UNIT 5: Chapter 11

TYPES OF REPRODUCTION

Asexual Reproduction does not include joining of gametes

BUD becomes new individual

Hydra

Bacteria

BINARY FISSION: Individual divides to produce new offspring

SPORES are asexual because they do not have to fuse to another cell.

PARTHENOGENESIS:unfertilized eggs develop into individuals (some fish, several insects, few species of frogs and lizards)

FRAGMENTATION: Pieces of organism develop into a new whole organism (Starfish and planarian are examples)

Sexual Reproduction

Process of sexual reproduction in which male and female gametes join to form a new cell (zygote).

Gametes are called sex cells.

Sexual versus Asexual Reproduction

Sexual• GAMETES fuse to form

zygote• VARIED GENES are

produced• Genetic VARIATION

allows for greater ADAPTATION in changing environment

Asexual• NO FUSION of gametes• Very little GENETIC

variation• MANY OFFSPRING in short

time without having to find mate

• LESS genetic variation causes LESS ability to ADAPT to changing environment

When gametes (egg and sperm) unite during fertilization, each gamete contributes one allele.

Meiosis

gametes

DRAW AND LABEL A CHROMOSOME

Identical chromatids

centromere

chromatid

Chromosome• DNA strands coiled around proteins• Formed during cell division• Contains specific genes on each

chromosome• Found only in nucleus of cell• Diploid organisms have 2 of each

chromosome, one from each parent• Haploid organisms have one of each

chromosome• Somatic chromosomes are in

different sizes and shapes• Number if chromosomes are

different for each species– Humans: 46 (23 pairs)

• Sex chromosomes ore either X or Y. – Females receive XX – males receive XY

Centromere

Identical Chromatids

chromatid

What is a chromosome?

Formation of chromosome

DNA = twisted ladder of nucleotides

DNA strands wrap around proteins

DNA/Protein strands coil tightly

Tightly coiled strands form chromosome

Where are chromosomes found?

• Chromosomes are found in the nucleus of our eukaryotic cells. • Many organisms have a different numbers of

chromosomes in their cells – Fruit fly 4 chromosomes– human 46 chromosomes

What are gametes?

• Also known as a sex cell.– 23 chromosomes in sperm (male gamete). – 23 chromosomes in egg (female gamete).

• Gametes are a product of meiosis. • Meiosis is the process which the number of

chromosomes cell is cut in half through the separation of homologous chromosomes. – 2 part process.– Process results in 4 gametes.

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MEIOSIS

Meiosis

Meiosis- The process of cell division in sexually reproducing organisms that reduces the number of chromosomes in reproductive cells from diploid to haploid, leading to the production of gametes in animals and spores in plants.

Meiosis

• Two phases of cell division (Meiosis 1 and 2)• Produces cells with half the number of

chromosomes (Haploid)– Haploid cells have one of each chromosome– Haploid cells (sperm and egg) join to form zygote

• Meiosis allows genetic variation– Joining of gametes makes new combinations of

genes for each new individual

Meiosis

Law of independent assortment

Alleles of different genes separate independently of one another

PpTt

PT PtpT pt

meiosis

4 haploid gametes: one of each chromosome

Meiosis summary: Produces 4 haploid cells

One chromosome from each parent

Homologous chromosomes•Same shape•Same size•Same type of genes•One from each parent

Crossing over occurs during Prophase I

New genetic combination

•creates new combination of genes•occurs between two homologous chromosomes

Gametogenesis: Process of making gametes

Most of cytoplasm from three cells is combined into one egg cell

When Meiosis Goes Bad…..

http://www.infertilityivfhouston.com/images/Sperm-morphology.jpg

Dangers of gametes without 23 chromosomes….

Mitosis vs. meiosis

What is a karyotype?

A karyotype is a set of photographed chromosomes grouped by pairs.

How is sex determined? VideoCHROMOSOMEPAIR ARE CALLED

SEX CHROMOSOMES:

IF XX= FEMALEIF XY= MALE

AUTOSOMESChromosomes #1-

22 are called

HUMAN MALE KAROTYPE HUMAN FEMALE KARYOTYPE

What happens if there are 3 chromosomes on your 21

chromosome?

ANSWER: DOWN SYNDROME

Down Syndrome

One chromosome from each parent

Homologous chromosomes•Same shape•Same size•Same type of genes•One from each parent

Which letter is an example of meiosis?Which letter is an example of

fertilization?

Letter A is an example of meiosis. Letter B is an example of fertilization.

DNA/Chromosomal Mutations

Deletion

Duplication

Inversion

Translocation

Chromosomal MutationsSection 12-4

Genetic Mutation?

Genetic Mutation?

IS albinism caused by a genetic mutation?

• Albinism (from Latin albus, meaning "white") is a lack of pigmentation in the eyes, skin and hair. It is an inherited condition resulting from the combination of recessive genes passed from both parents of an individual. This condition is known to affect mammals, fish, birds, reptiles, and amphibians.

Caused by a genetic mutation?

World’s Largest Feline

Is the caused by a genetic mutation?

• A clubfoot is a common birth defect.

Down Syndrome

• Defect (extra chromo) on the 21st chromosome.

If someone has a defect or disease, there is something wrong with

chromosomes in nucleus.

DISEASES

Can be caused by 2 things: 1. The environment that surrounds you.

2. Your inherited genes .

http://www.youtube.com/watch?v=kBfWybm0218&feature=related (vytorin commercial)

What disorders are sex-linked?

• Baldness• Hemophilia (free bleeder)• Duchenne Muscular Dystrophy (Progressive

loss of muscle)• Red-green colorblindness

These disorders are only found on the 23rd (sex) chromosomes.

Colorblindness

• Are you color blind?

What disorders are autosomal?

• Disorders caused by recessive alleles: albinism, cystic fibrosis, galactosemia, phenylketonuria(PKU), Tay-Sachs disease

• Disorders caused by dominant alleles: achondroplasia, huntington’s disease, hyperchlesterolemia

• Disorders caused by codominant genes: sickle cell anemia

Recall, alleles are different forms of genes.

Recessive Disorders

• Sickle Cell anemia (abnormal hemoglobin molecules– Results in poor blood circulation

• Tay-Sachs Disease (defective form of a brain enzyme)– Results in deterioration of nervous system in infants- early

death

• Cystic Fibrosis (Defective chloride-ion transport protein)– Excessive mucous accumulation in organs, especially lungs-

die young

Environmental Influences on Traits

• Hydrangea flower color is due to amount of acid in soil

• Temperature affects changes in fox color from winter to summer

• Darker parts of Siamese cat are a lower temperature, e.g., ears, nose, paws and tail

• Height in humans is influenced by temperature, such as internal environmental condition.

Pedigree ChartNormal female

Affected female

Carrier female

Normal male

Affected male

parents

Children in birth order

Reading pedigree charts:•If both males and females have disorder, then trait is autosomal (on other chromosomes)•If trait shows up mostly in males, then trait is sex-linked (on the X chromosome)