Biology Ch 14
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- Father of Genetics - 1800's
- Experimented with sweet pea plants
a character is an inhertible feature that varies among individuals (flower color)
each variant for a character is called a trait (white flowers, purple flowers)
pea flower pollen producing organs
egg producing organ
produces only the same variety as the parent plant
crossing two true breed varieties
- true breed parents are called the P generation (parent generation)
- hybrid offspring are called the F1 generation (first filial generation)
- filial is the latin word for "son"
- Allowing the F1 gen to self polinate resulted in the F2 generation (second filial generation)
in Mendel's time people believed that genes "blended" - red + white = pink
7 characteristic tested by Mendel
- Flower color: purple (P) white (p)
- Flower position: axial (A) terminal (a)
- Seed color: yellow (Y) green (y)
- Seed shape: round (R) wrinkled (r)
- Pod shape: Inflated (I) constricted (i)
- Pod color: green (G) yellow (g)
- Stem length: tall (T) dwarf (t)
- alternate variations of a gene
- purple or white flowers
- blue or brown eyes
- an organism inherits two alleles - one form each parent
- diploid cell has two sets of chromosomes - one form each parent. A genetic locus (location) is represented twice - once on each homolog of a specific pair of chromosomes
- device used for predicting the allele compostion of offspring from a cross between parent of known genetics
- Dominant - capital letter
- Recessive - lower case letter
- Put dominant characteristic on top - Homozygous dominant or Heterozygous
- Homo - same - identical alleles for the trait - Dom - PP
- Hetero - different - different alleles for the trait - Pp
- Homo - same - recessive - pp
- physical - what it looks like
- genotype - what genes it has
place - genese for the same trait line up on the alleles
Law of Multiplcation
Determines probability make punnett square for each trait and multiply the resulting fractions to determine probability
multiply the probability of one event by the probability of the other event
Mitosis Vs. Meiosis
- Produces an identical copy of a cell
- Produces diploid cells
- Produces two daughter cells
- One division cycle
- Produces non-identical cells
- Produces haploid cells
- Produces four daughter cells
- Two division cycles
homologues fail to separate correctly and you end up with an extra chromosome.
Examples include trisomy 21 (Down’s syndrome) where you have 3 copies of chromosome 21.
- A photographic representation of the chromosomes arranged from largest to smallest.
- Each chromosome has a particular number.
- The 23 pair are the sex chromosomes. In males XY and in females XX. In females one X is inactivated in each cell (Barr body).
- The rest of the chromosomes are called autosomes.
Nondisjunction of the sex chromosomes
- Klinefelters syndrome (XXY) produces sterile males with some female characteristics.
- Turner’s syndrome (XO) produces sterile females who are short in stature with neck webbing.
- Metafemale (XXX)
- Supermale (XYY)
- Heredity is not blending- there are discrete dominant and recessive traits.
- There are units or particles of heredity- we know now that these are genes.
- Every individual has a pair of these units for every trait- we have 2 alleles for every trait.
- These pairs separate in gametes- this happens during meiosis where one homologue goes to each daughter cell.
- Each gamete receives only one unit from each pair- they are haploid and combine to become diploid.
- probability that any one of two or more mutually exclusive events will occur is the sum of their
- individual probabilities.
•¼ + ¼ = ½ probability that child will be heterozygous
Domiant Trait Diseases
- Huntington Disease - neuro - degernerative
- Hypercholesterolemia - hyper bad cholesterol
- Marfan Syndrome - tall long -weak aorta
- Achrondroplasia - dwarfism
- These traits are controlled by more than one gene (pleiotropy)
- Look for a bell-shaped curve in the distribution of these traits.
- Examples include height and skin color.
- Only a partial dominance is exerted by an allele.
- Results in a blending.
- Examples: carnations and dogs, palomono horses
- Incomplete dominance notated by Pime ' ex R and R'
- not dominant and recessive - kinda equal
- This occurs when there are more than 2 alleles for a gene.
- Example: Blood Type where there are 3 alleles- A, B, and O.
- IA = Type A (IAi or IAIA)
- IB = Type B (IBi or IBIB)
- i = Type O (ii) is recessive
- Type AB (IAIB)
- O+ most commonO- second most commonB- least common
- Both alleles are expressed in a phenotype; one allele is not dominant to the other.
- This occurs in blood type and allows for the AB blood type.
- This also occurs in sickle cell anemia where those carrying the trait express some sickle cells.
- HBA = Normal blood
- HBS = Sicle cell
- These traits are located on the X and Y chromosomes.
- They may have nothing to do with sexual characteristics, for example color blindness.
- Since females have two X chromosomes (XX) and males only have one (XY). Males are more likely to show a trait located on the X chromosome, such as color blindness. Women would have to get two copies of the trait.
- Therefore, more males will show the trait.
- These traits cannot be passed from father to son as the father will only donate a Y chromosome to a son.
- Daughters can be carriers of the trait- meaning it is in their genotype but they don’t show it.
- Sons cannot be carriers- they either have it or they don’t.
- Examples: color blindness, hemophilia (Alexander, heir to the Russian throne), agammaglobulnemia (boy in the bubble), and a particular muscular dystrophy
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