Download Unit: Reproduction and Growth

Unit: Reproduction and Growth
Sections: Asexual Reproduction, Sexual Reproduction, Mendel and Heredity, Factors that Influence Human Growth and
Development
Key Words: reproduction, asexual, offspring, meiosis, mitosis, regeneration, budding, fission, cell division, spores,
DNA, bacteria, clone, gene, sperm, egg, pollination, stigma, anther, ovum, chromosome, heredity, trait, dominant,
recessive
Essential Questions: (by section)
Asexual Reproduction
How do organisms reproduce asexually?
How is asexual reproduction different from sexual reproduction?
How similar are organisms that are produced through asexual reproduction?
Sexual Reproduction
-
How are gametes involved in sexual reproduction?
How do plants reproduce sexually?
How does sexual reproduction lead to species diversity?
Mendel and Heredity
-
What is heredity and who first proposed it?
How do organisms inherit traits from their parents?
How do scientists predict which genes as organism will inherit?
Why are some physical traits more common than others?
How do human select for certain traits in some organisms?
Factors that Influence Human Growth and Development
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How do smoking, alcohol use, drugs, and diet influence human embryo development and human
health?
What environmental and lifestyle factors determine human characteristics?
What genetic factors determine human characteristics?
What are genetic disorders?
Asexual Reproduction
Two main forms of reproduction
- Sexual
 Combines gametes (sex cells)
 Has 2 parents
- asexual
 does not involve the joining of gametes (sex cells)
 does not involve more than one parent
 makes an exact clone of itself
 budding



DNA replicates
itself
Growth attached to the parent with hereditary material
Yeast, mold, sponges
Fission
DNA moves to
opposite ends
Cell divides into 2
cells
2 identical cells are
created



sporulation
 Formation of spores
 Fungi, algae
 Regeneration
 The ability to replace damaged tissues
 Starfish, planaria
benefits
 highly efficient
 produces large numbers of offspring in a short period of time
downfalls
 eliminates/limits genetic variation
 reduces chances for a population to adapt to environmental stress
Prokaryotic cells
http://www.bing.com/images/search?q=prokaryotic+cells&view=detail&id=1A828EBAF1BCBF715FCCE9C46AE0231C5571FF34&first=0
- Kingdom Monera
- DNA is free flowing in the cytoplasm (called
chromatin or hereditary material)
- Because it is a single-celled organism (selfcontained), it goes through asexual reproduction
o Cyanobacteria
o Bacteria
-
Bacteria can go through fission every 20 to 30 minutes
All identical cells from the parent
Within 24 hours, can equal the # of eukaryotic cells in the human body
Sexual Reproduction
-
formation of a diploid cell
 joining of 2 haploid cells (gametes)
 Increases diversity of traits for offspring
 Gives more variations to ensure survival of species
 No identical offspring
 created by the process of meiosis
 cells that have half the number of chromosomes as the diploid
 normal human cell – 46 chromosomes
 human gamete cell – 23 chromosomes

-
male human gamete (23) (sperm) + female human gamete (23)
(egg) = normal human cell (46)
 DNA – deoxyribonucleic acid
 Forms the strands called chromosomes
 Makes up “genes” – parts of the DNA strands that code for a specific
protein
 Phenotypes – physical traits
 Eye color
 Tongue-rolling
 Right hand/left hand
 Skin tone
 Hair color
 Genotypes – genetic make up coding traits
 Dominate and recessive traits
 Homozygous (same) and heterozygous (different)
once fertilization occurs – mitosis allows for growth
Fertilization
- mechanisms differ among plant and animal kingdom
- animals
 males deposit gametes on or near the female gamete
 land – internally via copulation
 water – externally because of fluid environment
- plants
 pollination – sexual reproduction among plants
 gymnosperms – “naked seeds”
 angiosperms – “flowering plants”
 male gametes on anthers – pollen grains
 transported by wind, water, or animals
 female gamete is attached to stigma
Mendel and Heredity
Heredity – the passing of traits from parent to offspring
- genes are made up of DNA
- located on chromosomes
Alleles – different forms of genes
- meiosis separates chromosome pairs
- gives each sex cell 1 allele for each trait
Genetics – the study of how traits are inherited through the actions of alleles
- Gregor Mendel – father of genetics
Austrian monk (1822)
Experimented with garden peas
Thought is was possible to predict outcome of flowers
“Experiments with Plant Hybrids”
Worked with large numbers to create more accurate predictions (30,000 pea plants over 8
years)
- Purebreds – an organism that always produces the same traits generation to
generation
- Cross-pollination – taking pollen off male and placing it on female reproductive
organ of different plant
• Dominant traits
 A factor that dominates or covers up the other traits
 The trait expressed/shown
• Recessive traits
 The trait that disappears (doesn’t show)
 Can show if recessive traits combine from both parents
- Punnett square
Dominant and recessive alleles are represented by letters
Capital letters represent dominant traits
Lowercase letters represent recessive traits
Genotype
o The genetic make-up of an organism
 Homozygous
• Two alleles exactly the same
• Ex. BB or bb
 Heterozygous
• One allele dominant and one recessive
• Ex. Bb
Phenotype
o The physical expression of a particular genotype
o Color, shape, physical attribute expressed
Incomplete dominance
- the production of a phenotype that is intermediate to those of the two homozygous parents
- ex. Crossing red homozygous flowers with white homozygous flowers and the offspring
expressing
- ex. pink flowers
- one allele is not able to be dominant over the other
Multiple alleles
- a trait controlled by more than two alleles
- ex. Blood type in humans
A, B, O
A & B are both dominant
O is recessive
Possible phenotypes:
o A – could have AA or AO
o B – could have BB or BO
o AB – only AB
o O – only OO
Polygenic inheritance
- when a group of gene pairs acts together to produce a single trait
eye color
fingerprints
height
weight
body build
shapes of features
skin color
- not limited to humans, plants have traits controlled by polygenic inheritance
- genes may influence a small amount but creates the variety that is expressed
many different skin tones in ethnic grouping
many different shades of blue eyes
many different shades of brown hair
Recessive Genetic Disorders
- sickle-cell anemia
homozygous recessive
red blood cells are sickle-shaped instead of a disc-shape
cannot deliver enough oxygen to cells of body
cannot move through vessels easily
usually found in tropical areas
heterozygous carriers do not express the trait but are known to be resistant to malaria
- Cystic fibrosis
Homozygous recessive
Thick mucus in areas of the lungs and digestive tract
Builds up in lungs and makes it hard to breathe
Reduces the flow of digestive enzymes to break down food
Mostly Caucasians
Sex determination
- x and y chromosomes
- females produce eggs with only x chromosome
- males produce sperms with x or y chromosome
Sex – linked disorders
- color-blindness linked to x chromosome
- more males with color blindness than females
all sexes have x chromosome
more chances to pass on trait
- sex-linked gene
an allele inherited on a sex chromosome
- hemophilia
an allele inherited on the x chromosome
Pedigrees
- a tool for tracing the occurrence of a trait in a family (leave blank area to fill in later)