Transcript Based on the study of probability

Genetics – the study of heredity
Based on the study of probability
(likelihood)
1. Why should we study genetics?
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Disease causes/treatments
Biotechnology – agriculture, animal husbandry
Breeding
Pedigrees- family lineages
Evolutionary trends
1.How are genes passed on to our
offspring?
2. Sperm carry ½ and eggs ½ of genetic code.
1. How are sperm & eggs produced?
2. Meiosis – germ cells
divide to produce haploid
cells (1 set of chromosomes)
3. Haploid =1N
2. Meiosis has 2 divisions
to reduce chromosome
number
2. What are the phases of meiosis?
• Meiosis I
– Prophase I- Crossing over of alleles occurs!
– Metaphase I- homologous chromosomes side by side
– Anaphase I- ho. chrom. separate (not chromatids)
– Telophase I- 2 cells with 2 chromatids of every
chromos.
• Meiosis II
– Prophase II- nothing happens
– Metaphase II- chromo align single file
– Anaphase II- chromatids pull apart
– Telophase II- 4 total cells w/ 1 copy of each chromo.
1N + 1N = 2N (a diploid cell)
46 XX= female
46 XY = male
23 pr homologous
chromosomes
What are the results of meiosis?
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4 cells
Genetically different
Haploid (1N)
In females, only one egg is used
What happens if chromosomes
don’t separate properly?
Nondisjuction results in trisomy or
monosomy
Dragon genetics activity to learn basic
vocabulary
Check for understanding following activity:
BB
Bb
Bb
Allele/gene
Genotype/phenotype
Mate your dragons
Punnett squares
• Designed to PREDICT outcomes (expected
ratios)
Single gene crosses
• monohybrid: Aa x Aa
• Or : AA x Aa
• Or Testcross: aa x A_____
Cystic fibrosis
• Due to a recessive allele (ff)
• Faulty membrane protein does not regulate
NaCl
• Cells create mucous around them/breeding
ground for bacteria
• Chromo #7
Huntington disease
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Due to a dominant allele
Late onset (35 years+)
Protein (huntingtin) destroys nerve cells
Due to a repeat of more than 21 CAG in a
gene
• Chromosome 4 (discovered in 1983)
• Maracaibo, Venezuela- Huntington research
Di- crosses probability problems
• Rh factors- effect on fetus- protein on RBC- rh
from RHESUS monkey- Rh neg makes
antibodies against Rh protein• Rh is important during fetal development
• Albinism- due to recessive alleles
Review terms
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Alleles/gene
Genotype/phenotype
Homozygous/heterozygous
Probability
Offspring/ F1/F2 generations
Dominant/recessive
Quiz
• 1. Explain how an allele is related to a gene.
• 2. What is the relationship between a
genotype and a phenotype?
• 3. Which of the following combinations are
homozygous? BB Bb bb
• 4. T-tall t – short Y –yellow y- green
• Cross a plant that is heterozygous tall and
homozygous for green seeds with a plant that
is short and is also homozygous for green
seeds.
• List the genotypes and ratios for the above
cross.
• List the phenotypes and ratios for the above
cross.
Codominance
• Both alleles of a gene express themselves=
both proteins are produced
• Examples:
– AB blood type (protein “A” and protein “B”)
– Sickle cell trait ( point mutation in hemoglobin)produces 3 phenotypes- normal, trait, anemia
Blood type importance
Your immune system makes antibodies against
foreign proteins.
Antibody A attacks blood type A
Antibody B attacks blood type B
Antibodies A & B attack blood type AB
Antibodies A & B DO NOT attack blood type O
blood types- multiple alleles
Phenotype (protein)
• Blood type A
Genotype (alleles)
• AA or AO
• Blood type B
• BB or BO
• Blood type AB
• AB
• Blood type O
• OO
Blood type lab
• Antibodies can cause blood to clump
(agglutinate)
• This is how blood is “typed” for accuracy for
transfusions.
What is the importance of sickle
cell trait?
• Evolutionary advantage to survive Malaria
• “heterozygote” advantage- NS (trait)
• “S” cells sickle and the protozoan is killed
Video clip on sickle cell evolution
http://www.pbs.org/wgbh/evolution/library/01/2/l_012_02.html
Normal RBCs vs. Sickle RBCs
phenotype
• Normal blood cells
genotype
• NN
• ½ normal & ½ can sickle
• NS
• all can sickle
• SS
Incomplete dominance
• 2 alleles “blend” their traits and produce a 3rd
phenotype
• Examples:
– Palamino horses (ncomplete & polygenic)
– Tay-Sachs enzyme levels (enzymes, some
enzymes, no enzyme)
Some flowers
X linked genes
• Genes that are located on the X chromosome
only
• Examples
– Hemophilia
– Red-green color blindness
– Duschene muscular dystrophy
– Calico cats
– ALD (Lorenzo’s oil disease)
hemophilia
• Hemophiliacs lack protein factors for clotting.
Pedigrees
Red – green color blindness
Muscular dystrophy
Image of Calico cat- x linked &
epistatic genes
Epistatic genes
• Genes that “cancel” out other genes
Pedigrees
• Family trees that show inheritance
Environmental effects on genes
Polygenic inheritance
• More than one gene codes for a trait
Examples”
skin color, eye color, height, hair color
Genes are “additive”
Chromosomal changes
Turner’s Syndrome
Occurs in females. Missing an entire X
chromosome.
Non-working ovaries (no menstrual cycle)
Short stature and webbed neck
Increased risk of heart and cardiovascular
problems
Triple X Syndrome
• Three X chromosomes
• Only one X chromosome is active at a time
(little adverse effects)
• Tall stature, small head, fold in skin
• Learning disabilities. Low self esteem
• Fertile
Poly X Syndrome
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XXXX and XXXXX
Similar symptoms to XXX
Small head and jaw
Very tall stature
Irregular shaped heart and lungs
Very low IQ 10-15
Klinefelter Syndrome
• XXY
• Common 1:500 male births
• Decreased testosterone levels
– More female characteristics
Decreased fertility
Slow development as infants and during puberty
XYY Syndrome
• Increased testosterone production
– Rapid growth
– Large muscle mass (without exercise)
– Increased aggression ( still up for debate)
– Normal IQ’s and fertile.
XXYY Syndrome
• Similar symptoms to Turners Syndrome but in
males
• Mentally Chellenged
XXXY, XXXXY, XXXXXY
• Very rare cases, caused by mutations in the
formation of gametes.
• Similar symptoms to Turners Syndrome (extra
X).
• Retardation
• Short life span
• Sterility
• Can only be diagnosed with Karyotyping
(what is that?)
timeline
• Genetics introduction to Mendel & vocabulary
via dragon genetics
• Single gene Punnetts
• Multiple gene Punnetts
• Codominance
• Incomplete dominance