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Unit 4 G7: Genetics
Transcript of Unit 4 G7: Genetics
How does the interior determine the exterior?
SEX CHROMOSOMES contain genes that determine the gender on an individual.
Remaining chromosomes are called AUTOSOMES.
Karyotype: # and appearance of chromosomes.
Sex-linked traits mostly occur on X chromosome.
Males who carry recessive allele on X chromosome will exhibit sex-linked trait because they only have one X chromosome.
Sex Linked Trait Virtual Lab Questions
Setting: 1950's, Cambridge University
Suspects: James Watson Francis Crick, Rosalind Franklin
Watson and Crick had a model, but Franklin's x-ray diffraction photographs of DNA crystals helped solidify model.
DNA is a nucleic acid made up of long chains of nucleotides.
Nucleotides consist of 3 parts: a 5-carbon sugar, a phosphate group and nitrogenous base.
Five carbon suger = deoxyribose
Similar to a spiral staircase; each full turn has 10 nucleotide pairs.
Detecting Genetic Disease
Genetics: the field of biology devoted to understanding how characteristics are transmitted from parents to offspring.
In 1851 he studied at the University of Vienna.
Most famous for experiments on garden peas.
Observe 7 pea characteristics (traits):
Trait: genetically determined variant of a characteristic, such as yellow flower color.
Mendel Pea Plant Key Words:
1.) True-Breeding: plants that are pure for a trait; always produce that offspring when they self-pollinate
2.) P generation: true-breeding parents
3.) F1 Generation: offspring of P generation
4.) F2 Generation: offspring of F1 generation
Each of the traits came in 2 varieties.
An allelle is any gene that gives rise to
more than one trait.
It's located at a specific position on a chromosome.
Ex: Tall gene and short gene are
different allelles for height.
Homozygous: 2 alleles for one trait are the same (PP)
Heterozygous: 2 alleles are different (Pp)
Genotype: organism's genetic make-up
Phenotype: organism's physical appearance
A convenient graphical model to the genotypes of the parental gametes and all possible offspring.
Sugar and phosphate group are idetical in all DNA
The nitrogenous bases may be any of 4 kinds: thymine, cytosine, adenine, guanine (A,T,G,C)
Base pairing rules: C-G go together, A-T go together
Name the complimentary base pairs to the following strand: ACCTGTGAGAC
Let's make an Origami DNA!
DNA replication normally occurs with great accuracy.
Only one error per billion of paired nucleotides.
Equivalent to typing abook 1000 times and making only one error.
A change in the nucleotide sequence is called a mutation. They can have serious effects on the function of a gene.
Example: Cancer - mutations can affect genes that control how a cell divides and can lead to abnormal masses called tumors.
The Human Genome Project
The entire gene sequence of the human genome is
known; completed in 2003.
Biologists have diciphered the order of 3.2 billion base pairs in the 23 human chromosomes. That is over 20,000 genes.
The human genome is so large it would take a person almost 10 years to read the total sequence aloud.
Potential benefits: find disease treatments, identify mutations linked to cancers, advancements in forensics, livestock breeding improvements,
Criterion F. Attitudes in Science
1900's Thomas Hunt Morgan began experimenting.
Flies have 4 chromosomes.
Observed that 3 pairs in females and males are the same, but 1 pair differed in size and shape.
Females had XX and males had XY.
X and Y chromosomes are called sex chromosomes.
1. The genotype of a red-eyed male fruit fly would be:
E. None of the above
2. Sex-linked traits:
E. None of the above
3. A monohybrid cross analyzes:
A. One trait, such as eye color
4. A female with the genotype XRXr:
E. B & C
5. In T.H. Morgan's experiments:
D. A & B only
6. In this laboratory exercise:
A. The Punnett square will allow you to predict the traits
of the offspring created in your crosses.
7. In a cross between a homozygous red-eyed female fruit fly and a white-eyed male, what percentage of the female offspring is expected to be carriers?
8. In a cross between a white-eyed female and a red-eyed male:
C. All females will have red eyes.
9. In human diseases that are X-linked dominant, one dominant allele causes the disease. If an affected father has a child with an unaffected mother:
A. All males are unaffected.
Most human characteristics are POLYGENIC - they are influences by several genes. i.e. skin color, 3-6 genes.
Codominance: both traits are equally dominant and will in the phenotype. i.e. blood type, A, B, AB, O.
Incomplete dominance: individual displays a trait that is intermediate between the two parents. i.e. wavy hair
During pregnancy a woman can have a genetic screening that involve karyotypes, blood tests, or direct DNA tests - 200 disorders detected.
Amniocentsis: doctor removes some amniotic fluid from the amnion, the sac that surrounds the fetus between 14-16 weeks of preganancy.
Chorionic Villi Sampling: doctor takes cells that grow between the mother's uterus and placenta between the 8th -10th week.
Sickle Cell Anemia
Gradual brain deterioration by middle age.
Causes loss of control of bosy movement.
1 in 10,000 births affected
Mucus clogs lungs and pancreas. Difficulty breathing and lung infections are common.
1 in 900 French Canadians
1 in 2000 Europeans
Clubbing of fingers due to low oxygen levels.
Organ damage fue to impaired blood flow.
Vessels get clogged due to sickle shaped cells.
1 in 500 African Americans
Deterioration of central nervous system resulting in death in early childhood.
1 in 600 Jews of European
Disorder of the connective tissue. Long limbs, loose joints, deformed spine, crowded teeth, severe nearsightedness
1 in 5,000 people
Externally female, but the sex chromosomes are XY (male), no or delayed puberty, lack ovaries
1 in 30,000 people
Prolonged internal or external bleeding due to ineffective blood clotting
1 in 30,000 people
MYP Statement of Inquiry:
Identity forms due to internal and external influences in the environment.
What is DNA and why is it important?
How can we predict traits of offspring?
To what extent does the interior determine the exterior?