Chapters 11-12 Flashcards
Differentiate between the “blending” hypothesis and the “particulate” hypothesis of genetic inheritance. Which did Mendel support?
Blending-Taking two things and making it into one while the particulate hypothesis of genetic inheritance states that parents pass discrete heritable genes to their offspring.
Mendel supported the particular hypothesis.
Mendel used the term “character” to describe a heritable feature that varies among a population. What term do we now use? What about the term “trait” that Mendel used?
characters=genes
-trait= allele
Name three advantages of using pea plants for genetic study.
- Many different varieties (color/shape/ length) either or characteristic
- He could control the mating (which plant mated with another)
- Produces many offsprings
What is “true-breeding”?
Plants that produce an offspring of the same variety when they self-pollinate/reproduce. Same phenotype (homozygous)
What is hybridization?
Mating two different true breeding organisms/varieties
Name 4 of the 6 characters that Mendel studied in his pea plants.
1.plant size. 2. flower color. 3. seed color 4. seed shape
Differentiate between the P, F1 and F2 generations.
p= parent F1= offspring of the parent F2= offspring of the F1 generation (offspring) -second generation
What did Mendel obtain for F1 offspring when he crossed a true breeding purple and a true breeding white flowered pea plant?
All purple flowers
What did Mendel cross to obtain his F2 generation?
Two of the purple flower offsprings from generation 1 (self or cross pollination)
What ratio of purple to white flowers did Mendel obtain in his F2 offspring?
3:1
Differentiate between a “gene” and an “allele”.
gene- = an particular trait (blue eyes) Allele- a form of a gene (hair color)
How many alleles are inherited for each gene? Why?
2, one from each parent
What is the difference between a dominant and a recessive trait? What do we use in genetics to represent dominant and recessive alleles?
- Dominant trait is a trait that is expressed while a recessive trait is a trait that will only show up if the whole gene is recessive.
- Recessive= two lowercase letters Dominant= 2 capital letters or one capital letter and a lowercase letter
Differentiate between homozygous and heterozygous and give an example.
homozygous= 2 of the same letter(AA or aa) heterozygous- 1 lowercase and one capital letter (Aa)
What is the law of segregation?
When two alleles for a heritable character separate during gamete formation. End up in different gametes
Differentiate between genotype and phenotype.
Genotype- genetic makeup phenotype-physical appearance
If you are uncertain of an individual’s dominant genotype, what can you do to figure it out?
You do a testcross between the individual and a homozygous recessive individual of the same type.
Differentiate between a monohybrid and a dihybrid cross.
Monohybrid- individuals heterozygous for one character
dihybrid= individuals heterozygous for two characters
What did Mendel observe in the offspring of his YyRr x YyRr cross? What were the phenotypic ratios? Make sure you understand how to perform a dihybrid (or two-factor) cross.
Phenotypic ratio 9:3:3:1
What gametes would result from the genotype YyRr?
YR, yr, yR, yr
What is the law of independent assortment?
Each pair of alleles segregates independently from any other pair during gamete formation
How did the dihybrid cross prove independent assortment?
The alleles for the color of the seed did not affect the shape of the seed
Mendel stated that each pair of alleles is what assorts independently. We now know this isn’t entirely true. What would be a correct statement?
Each chromosome segregates independently from any other chromosome
Why can probability be used in genetics?
To determine how likely two independent events will happen together
A homozygous recessive for seed shape and color (rryy) is crossed with one that is heterozygous for seed shape and color (RrYy). What is the probability the offspring will be RrYy? (Use the rule of multiplication instead of the Punnett square).
¼
Differentiate between complete dominance, incomplete dominance and codominance. Give an example of each.
Complete dominance- phenotypes of the heterozygous and dominant homozygous are identical and dominant (Rr and RR will both be round)
Incomplete dominance= the phenotype of f1 is between its parents (ex: parents red and white -offspring=pink)
codminance= two dominant alleles affect the phenotype in separate and distinguished ways (ex; parent 1= stripes parent 2=dots- offspring-strips and dots)
Explain the inheritance pattern of multiple alleles.
You inherit 2 alleles despite how many there are
How many alleles exist for human blood type? Which are dominant? Recessive?
- 3 alleles (Ia, Ib, and i)
- dominant: Ia and Ib
- Recessive: i
List the 6 different genotypes that can occur in human blood type.
1.Ia Ia 2.Ia i 3. Ib Ib 4. Ib i 5. Ia Ib 6. Ii
If one parent is type A and another has type B, is it possible for them to have a child with O blood? Why or why not?
Yes if both parents are heterozygous. There would be a ¼ chance.
Define pleiotropy and give an example.
When a gene has multiple phonetic effects (ex: cystic fibrosi)
One gene-multiple effects
Define epistasis and give an example.
When a gene at one locus(positon) affects a gene at a different locus (BBcc will have no color but BBCc or BBCC will give a black color)
What are quantitative characters? Give an example in human genetics.
Characters that vary along a continuum (skin color )
What is polygenic inheritance?
An additive effect of two or more genes on a single phenotype
One trait many genes
When phenotype is influenced by both genetics and environment, those characters are called ________________.
Multifactorial characters
What is a pedigree? How can they be used in genetics?
A family tree that describes the interrelationship between parents and children across generations
-to find the inheritance of a particular trait and the probability of passing a diseases
Describe the following genetic disorders. Indicate whether they are dominant or recessive
Cystic Fibrosis Sickle cell disease- Tay-Sachs disease Achondroplasia- Huntington’s Disease
- Cystic Fibrosis- defective or absent chloride transport channels (symptom-mucus build up) Recessive
- Sickle-Cell Disease- not able to absorb enough oxygen, cells compact recessive
- Tay-Sachs disease is fatal; a dysfunctional enzyme causes an accumulation of lipids in the brain both recessive
- Achondroplasia- causes dwarfism Dominant
- Huntington’s Disease- degenerates the nervous system (after ages 35-45) Dominant
The chromosome theory of inheritance brought together what two realms of science due to the noticeable parallels between the two?
-Cell biology
Differentiate between the law of segregation and the law of independent assortment.
- Law of segregation= When two alleles for a heritable character separate during gamete formation. End up in different gametes (anaphase 1)
- Law of independent assortment-Each pair of alleles segregates independently from any other pair during gamete formation (independent alignment (metaphase 1)
What is meant by a “gene locus”?
The specific location of a gene
Genes located on the same chromosome are said to be ___________ and will be inherited _________________.
- linked genes
- together
What characteristics of fruit flies make them convenient for genetic study?
- They produce many offspring
- A generation can be bred every two weeks
- They have only four pairs of chromosomes
Differentiate between wild type and mutant type.
- Wild type=normal, phenotypes that were common in the fly populations
- mutant type-Traits alternative to the wild type
What evidence of gene linkage did Morgan see in his fruit flies?
-only males had white eyes
When Morgan mated male flies with white eyes with female flies with red eyes, what did he observe in his F1 generation? F2 generation?
-The F1 generation all had red eyes
-The F2 generation showed the classical 3:1 red:white
ratio, but only males had white eyes
What is a sex-linked gene?
-A gene that is located on either sex chromosome
Name three examples of sex-linked disorders.
- Color blindness (mostly X-linked)
- Duchenne muscular dystrophy
- Hemophilia
Why are sex-linked disorders more common in males?
Because males only carry one x chromosome
What is X-inactivation? What is a Barr body?
x-inactivation=one of the two X chromosomes in each cell is randomly inactivated during embryonic development
Barr body= inactive x chromosome
Based on your knowledge of x-inactivation, explain the tortoise shell coloration in cats. (Black/Orange fur).
-the inactive x on a cat doesn’t express the gene instead the active gene is expressed. On different cells the inactive x and active x change and the cat has multiple colors expressed.
What is genetic recombination?
-the production of offspring with combinations of traits differing from either parent
When Morgan did his crosses with body color and wing shape, what led him to believe those two traits are linked?
-genes of the parental types had a higher ratio
In Morgan’s cross between fruit flies with gray body color, normal wing shape with black body, vestigial wing shape he saw most of his offspring had the same
In Morgan’s cross between fruit flies with gray body color, normal wing shape with black body, vestigial wing shape he saw most of his offspring had the same phenotypes as the parents. This was an indication the body color and wing shape were linked. How then, is it possible to also get recombinants of body color and wing shape, such as a gray body with vestigial wings?
-Crossing over
What frequency (percent) of recombination is observed for any two genes on different chromosomes?
50% frequency
What is a linkage map? How does it differ from a cytogenetic map?
-Linkage map= a genetic map of a chromosome based on recombination frequencies
It differs from a cytogenetic map because a cytogenetic map tells the location of genes in respect to chromosomal features
What is a “map unit”?
The distance between genes (one map unit=1% recombination frequency)
When is crossover more likely between two genes on the same chromosome? Less likely?
More likely= 50 map units away or more
Less likely= less than 50 map units away
What is nondisjunction?
-When pairs of homologous chromosomes do not separate normally during meiosis
When is nondisjunction more detrimental – Meiosis I or Meiosis II? Why?
-Meiosis 1 because its when homologous pairs line up and separate
What is aneuploidy? Give an example of a disorder resulting from autosomal aneuploidy and sex chromosomal aneuploidy.
When nondisjunction occurs from fertilization involving gametes
Autosomal aneuploidy and Sex chromosomal aneuploidy= Klinefelter syndrome
Differentiate between a trisomic zygote and a monosomic zygote.
trisomic zygote= zygote has three copies of a particular
chromosome
-monosomic zygote= zygote has only one copy of a
particular chromosome
What sex chromosomes are inherited in a person with Klinefelter’s? Turners’?
Klinefelter syndrome- extra chromosome in a male, producing XXY individuals
Turner syndrome- produces X0 females, who are sterile
What is polyploidy?
-a condition in which an organism has more than two complete sets of chromosomes
Name the 4 types of chromosomal mutations that result in alterations in chromosome structure.
- Deletion: removes a chromosomal segment
- Duplication: repeats a segment
- Inversion: reverses orientation of a segment within a chromosome
- Translocation: moves a segment from one chromosome to another
Explain the 4 types of chromosomal mutations.
- Deletion: removes a chromosomal segment
- Duplication: repeats a segment
- Inversion: reverses orientation of a segment within a chromosome
- Translocation: moves a segment from one chromosome to another
Name a disorder that results from alteration of chromosome structure.
Cri-du-chat (cat’s cry)
