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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
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
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- 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
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
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
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
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.
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.
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.
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)