Chapter Twelve Flashcards
Chapter 12
What are genes?
They are segments of DNA that encode info that are used to build specific proteins.
What is an allele?
they are alternate forms of a gene
example is R and r, which are the same gene but just different forms
Who is the father of genetics?
Gregor Mendel
worked with garden peas to study heredity
what is phenotype?
the actual physical appearance of a organism
what is genotype?
the genetic constitution of an organism
What is a dominant allele?
it is an alternate form of a gene that is expressed, and their effects are exerted when they are present
they code for functional proteins
What is a recessive allele?
it is an alternate form of a gene that isn’t expressed when the dominant allele is present.
they code for non functional proteins
What does homozygous mean?
when the two alleles (one from mom and one from dad) are the same HH or hh
What does heterozygous mean?
when the two alleles are different, one dominant and recessive Hh
Explain the (P), (F1), and (F2) generations in Mendel’s original round and wrinkled seeds.
P generation started with a dominant homozygous and a recessive homozygous
F1 the resulting offspring of P is all heterozygous, which are self-bred
F2 the result of two heterozygotes gives the 3 to 1 phenotypic ratio of and the 1 to 2 to 1 genotypic ratio
Explain the P, F1 and F2 in the dihybrid cross of seed shape and color.
P in this scenario was the homozygous dominant RRYY and the homozygous recessive rryy
F1 resulting from P was all heterozygotes RrYy
F2 shows a 9:3:3:1 phenotypic ratio, but 9 different genotypes show in a 16 punnet square in which the RY, Ry, rY, and ry are bred
What was the significance of Mendel’s first law?
that our genes occur in pairs and segregate from each other during formation of gametes
the law of segregation entails that two copies of a gene separate during gamete formation (one copy per sex cell)
What was Mendel’s second law?
the law of independent assortment which states that copies of different genes on the gametes assort independently shown by the dihybrid cross
Who do offspring inherit their alleles from?
they inherit them one from each parent and they are either heterozygous or homozygous
How should the genotype of a father (HhBb) be represented on a punnett square?
father should be on top and the four gametes should be HB, Hb, hB, hb
How should the genotype of a mother HHbb be represented on a punnett square?
mother should be on the side and the four gametes should be Hb, Hb, Hb, Hb
What is the multiplication rule?
the probability of two independent events happening TOGETHER can be found by multiplying the probabilities of the events together
eg. getting a heads two times flipping coins is a 1/4 odds (1/2 x 1/2)
What is the addition rule?
the probability that an event can occur in two different ways is just the sum of the separate probabilities
eg. chances of getting a heads OR a tails in one turn (1/2 + 1/2) = 1
What is true breeding?
when the parental generation has the same exact genotype in order to show the same phenotype in the next generation
e.g would be HH with another HH or yy with yy
What is incomplete dominance?
when alleles are neither dominant or recessive, so heterozygotes have a new intermediate phenotype,
alleles have not blended and the original phenotypes will show up later down the road
MORE PHENOTYPIC DIVERSITY
what is co-dominance?
when more than one allele codes for a functional protein,
dominant R red allele and dominant W white allele come together to have red and white spots or vice versa
What is wild type?
it is the allele present in most of the population.
What is a mutation?
it is a stable inherited change in genetic material
-alleles that are not wild types are mutant alleles.
Where do both wild type and mutant type alleles reside?
the same locus
What is a locus?
it is the specific location of a gene on a chromosome
What are linked genes?
since many genes are found on a single chromosome, when genes are physically linked they reveal inheritance patterns that aren’t mendelian
example is the fruit flies where color of bodies and size wings were linked genes and so the recessive pairs and dominant pairs showed a different ratio than the 1 to 1 to 1 to 1 predicted
What is Pleiotropic?
is when one allele has multiple phenotypic effects
example would be Marfan syndrome, which is caused by variation in the FBN1 gene, people with Marfan syndrome tend to be tall with long thin fingers, toes and limbs.
What is epistasis?
is when the phenotypic expression of one gene is influenced by another gene
example is that alleles for black and brown dogs aren’t expressed unless the E allele is expressed bbEe and BbEE are brown and black dogs respectively
What is the effect of the environment on phenotype?
Light, temperature, nutrition, etc. effect the expression of genotype
What is significant about Siamese cats and rabbits in reference to environmental effect ?
There is point restriction coat patterns in them where enzymes that produce dark fur are inactive at higher temps
therefore the nose ears are cooler so they appear darker
How can prokaryotes exchange genes?
they exchange genes when the DNA of a donor cell passes to recipient cell through conjugation
DNA often lines up and crossing over occurs, changing the makeup.
What are plasmids?
they are small circular chromosomes that can
1. move between cells during DNA transfer
2. can replicate independently of main chromosome
What kind of genes do plasmids contain?
- genes that code for unusual metabolic functions, like breaking down hydrocarbons
- genes that code for antibiotic resistance
- genes that code for making a sex pilus
