Final Exam Flashcards
What is the process of producing egg and sperm cells?
Gametogenesis
In egg cells and sperm cells the chromosomes are located in what organelle of the cell?
Nucleus
What is it when a sperm cell from a male and an egg cell from a female unite to form a single cell called a zygote?
Fertilization
What is a zygote?
A diploid cell resulting from the fusion of two haploid gametes
How does a zygote divide?
Mitosis
What are the two types of chromosomes in a man?
X and Y
What are the types of chromosomes involved in sex determination?
Sex chromosomes
What are the two types of sex chromosomes?
Egg (X)
Sperm (X or Y)
How many sets of chromosomes are there in a human somatic cell?
23
How many chromosomes are there in a somatic cell?
How many from the father?
How many from the mother?
46
23
23
Of the 46 chromosomes in humans how many are autosomes?
How many are sex chromosomes?
44
2
How many sets of chromosomes are there in a human gamete?
23
How many autosomes are there in sperm and eggs cells? What about sex chromosomes?
22
1
How 44+XX zygote produced?
Egg: 22+X
Sperm: 22+X
How is a 44+XY zygote produced?
Egg: 22+X
Sperm: 22+Y
Reduction division in which the number of chromosomes per cell is _____.
Cut in half
Meiosis involves _____ divisions producing a total of _____ daughter cells.
Two
4
Meiosis occurs in what organ in females? What is the process called?
Ovaries
Oogenesis
Meiosis occurs in what organ in males? What is the process called?
Testes
Spermatogenesis
The cells in the ovary that are destined to become egg cells are called _____.
Are they diploid or haploid?
How many chromosomes are there?
Primary oocyte
Diploid
46
When does meiosis I occur in females?
Embryonic development
When does meiosis II occur?
Fertilization
The cells in the testes that are destined to become sperm cells are called _____.
Are they diploid or haploid?
How many chromosomes are there?
Primary sperm
Diploid
46
What stage precedes meiosis I?
What events occur during this stage?
Interphase
Growth
DNA synthesis
Etc
What are the four phases of meiosis I?
Prophase I
Metaphase I
Anaphase I
Telophase I
Cytokinesis
What are the four phases of meiosis II?
Prophase II
Metaphase II
Anaphase II
Telophase II
Cytokinesis
What is a pair of homologous chromosomes?
One member is obtained from the mother and the other from the father
Same size and shape
What are the events in prophase I?
Chromosomes coil tighter
Synapsis
Crossing over
What is crossing over in meiosis I?
Occurs during prophase I when homologous chromosomes pair up and exchange genetic material
What is chiasma?
X shaped regions where crossing over occured
Crossing over in meiosis I increases the ______ of the gametes.
Genetic variability
What are the events in metaphase I?
Tetrads line up at the metaphase plate
What is a tetrad?
A four part structure that consists of two homologous chromosomes, each composed of two identical chromatids
What separates in anaphase I?
Homologous chromosomes
What are the events in telophase I?
Each half of the cell has a haploid set of chromosomes.
Cytokinesis usually occurs simultaneously, forming two haploid daughter cells
What are the events in prophase II?
Spindle apparatus forms chromosomes (still composed of two chromatids).
Moves towards metaphase plate
What are the events in metaphase II?
Sister chromatids are arranged at the metaphase plate.
What separates in anaphase II?
Sister chromatids
What are the events in telophase II?
Chromosomes arrive at opposite poles
Nuclei forms and chromosomes begin decondensing
What are the four unique events to meiosis?
Crossing over
Synapsis (pairing homologues)
Sister chromatids remain attached during anaphase
Suppression of DNA replication during interphase
1 parent = 4 daughter
N=2n
1st meiosis
2nd meiosis
2n
n n
n n n n
Starting with 48 chromosomes (2n). How many in meiosis I and II?
24 and 24
Crossing over occurs in homologous _____.
Non sister chromatids
Crossing over occurs where on a chromosome?
Only the tip not middle
What are recombinant chromosomes?
Crossed over
What does 3 tetrads equal?
6 chromosomes= 12 chromatids
The segregation of the pair of alleles corresponds to the separation of _____ which occurs during _____ of meiosis 1.
Homologous chromosomes
Anaphase 1
When Mendel crossed contrasting, true breeding white and purple flowered pea plants all of the F1 hybrids were _____.
Purple
When Mendel crossed the F1 hybrids, many of the F2 plants had _____ flowers but some had _____ flowers.
Purple
White
The F1 hybrids had the recessive allele, but why were all of the F1 plants purple?
The dominant allele (purple) masked the recessive recessive allele (white).
Was the factor for white flowers diluted or destroyed in the F1 offspring? Explain.
No, because the gene was still there and it was just hidden by the dominant allele.
Mendel discovered a ratio of _____ in the _____ generation.
3 purple : 1 white
F2
What are the possible genotypes of the individual with a dominant phenotype?
AA or Aa
What will be done to know if the individual is homozygous or heterozygous dominant?
A test cross is performed
What is a test cross?
Breeding the mystery individual with a homozygous recessive individual.
If the result of the test cross shows only the dominant phenotype, the mystery individual is _____.
PP (homozygous dominant)
If the test cross shows 1:1 ratio dominant and recessive phenotypes, the mystery individual is _____.
Pp (heterozygous dominant)
During meiosis, is the segregation and assortment of the alleles for shape dependent on the segregation and assortment of the alleles for color?
No, because they are inherited separately and randomly
What happens during meiosis?
Dominant will produce only YR and other will produce only yr.
What is the phenotype of the F1?
RrYy (round and yellow)
If F1 hybrids are mates with each other, what are the different types of gametes that will be produced?
RY, Ry, rY, ry
What is the phenotypic ratio of the F2 offspring?
9:3:3:1
Complete dominance
Occurs when phenotypes of the heterozygote and dominant homozygote are identical
Incomplete dominance
The phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties
Codominance
Two dominant alleles affect the phenotype in separate, distinguishable ways
Two of the normal individuals have the recessive allele, why are those individuals not showing the recessive trait?
They are masked by the dominant allele
When a dominant allele coexists with a recessive allele in a heterozygote, do they actually interact?
No
In the cross between plants with red flowers and plants with red flowers and plants with white flowers, what is the phenotype of the F1 hybrids? Explain why.
Pink, because it is heterozygous where neither color is fully expressed
When the F1 hybrids are crossed, are there offspring showing the parental (P1) phenotypes?
Yes showing both
In codominance, two alleles at one locus produce phenotypes that are both present in the _____.
Heterozygote
In ABO blood group, what are the alleles that are codominant?
AB
For blood type AB, is there a homozygous genotype?
No
Describe codominance in the feathers of a chicken.
Black and white if one parent is black and one parent is white
Describe codominance in the coat color in cows.
Same as chicken
Describe codominance in the camellia flowers.
Will display speckles of both colors
In ABO blood group, what are the three alleles that determine the four phenotypes?
A, B, O
The A allele is dominant over the _____ allele.
O
The B allele is dominant over the _____ allele.
O
The A and B alleles are _____.
Codominant
What are the genotypes of the individuals with;
Blood type A:
Blood type B:
Blood type AB:
Blood type O:
AA, AO
BB, BO
AB
OO
What is polygenic inheritance and give two examples?
Multiple genes are involved in controlling the phenotype of a trait
Phenotype is an accumulation of contributions by multiple genes
Traits show continuous variation and are referred to as quantitative traits
Example: human height
What is pleiotrophy and give one example?
Refers to an allele which has more than one effect on the phenotype
Difficult to predict, because a gene that affects one trait often performs other unknown functions
Example: This can be seen in human diseases such as cystic fibrosis and
Marfan syndrome
Multiple symptoms can be traced back to one defective allele
What is epistasis?
Gene at one locus alters the phenotypic expression of a gene at a second locus
How does epistasis affect grain color?
Allowing one gene to mask the expression of another gene involved in pigment production
How does temperature affect the coat color of Siamese cats?
Coat color in Himalayan rabbits and Siamese cats.
Gene produces an enzyme that allows pigment production only at temperatures below 30 degrees Celsius.
What is pedigree and what can be its uses?
Family tree that describes the interrelationships of parents and children across generations
Inheritance patterns of particular traits can be traced and described using pedigree
Can also be used to make predictions about future offspring
Separation of retreads occurs when?
Anaphase 1
Particulate inheritance
One or the other, not a blend of traits
At present the “hereditary factors” that Mendel was referring are called _____ and they are located in the _____.
Genes
Chromosomes
What is a gene?
A specific segment of DNA that contains the instructions for making a particular protein
DNA is contained in what structures in eukaryotic cells?
Nucleus
Chromosome theory states that _____.
Mendelian genetics have a specific loci (positions) on chromosomes
Chromosomes undergo segregation and independent assortment
What accounts for mendels law of segregation and independent assortment?
The behavior of chromosomes during meiosis
Law of segregation
Homologous pairing and segregation of homologous chromosomes during anaphase 1 leading to segregation of alleles into separate gametes
Law of independent assortments
The alleles of two or more different genes assorted independently of each other during meiosis such that random combination of the genes from each pair winds up in the gametes. This occurs because there are various ways the homologous are aligned in the metaphase plate during metaphase 1
What are the two sex chromosomes?
X and Y
What gene is responsible for the development of the testes?
SRY gene on the Y chromosome
Sex linked traits are governed by genes found on the _____ chromosomes.
Sex
What are the two types of sex linked traits?
X Linked
Y linked
Give examples of X linked.
Color blindness, hemophilia, muscular dystrophy
Give examples of Y linked.
Hypertricosis
For a recessive X linked trait to be expressed, females need _____ copies of the allele (homozygous) and males need only _____ copy of the allele (Hemizygous).
Two
One
Where are sex linked recessive disorders much more common? Males or females? Why?
Males, because they are hemizygous (one and affected)
The color blind father will transmit the mutant allele to all his _____ but not to his _____.
Daughter
Son
Mother can pass the sex linked alleles to both _____ and _____.
Daughter
Son
The man with hypertrychosis will transmit the trait to _____.
Males
What is genetic hypertrichosis?
Hairiness of the external ear
What are sex influenced traits?
They are governed by genes found on the AUTOSOMES but dominant in one sex and recessive in the other
Examples of sex influenced traits?
Pattern baldness in humans
What are sex limited traits?
They are governed by genes found on the AUTOSOMES but expressed in one sex
Sex limited trait examples?
Feathering in chickens, milk production by females
Pattern baldness is caused by an _____ gene.
Autosomal
Allele B behaves as _____ in males but _____ in females.
Dominant
Recessive
Pattern baldness: females
BB?
Bb?
bb?
Bald
Non
Non
Pattern baldness: Males
BB?
Bb?
bb?
Bald
Bald
Non
Feather plumage in chicken is caused by an _____ gene.
Autosomal
Hen feathering is controlled by a _____ allele expressed in both sexes.
Dominant
Cock feathering is controlled by a _____ allele only expressed in males.
Recessive
Hen feathering or cock feathering: female
hh?
Hh?
HH?
Hen feathered for all
Hen feathering or cock feathering: male
hh?
Hh?
HH?
Cock
Hen
Hen
What is X inactivation in female mammals? What is the reason for X inactivation?
Most diploid cells have only one fully functional X chromosome
One of two X chromosomes in each cell is randomly activated during embryonic development
What is a Barr body?
Inactive X
If a female is heterozygous for a particular gene located on the X chromosome, she will be a _____ for that character.
Mosaic
The gene for orange and black fur in cats is located in what sex chromosome?
Orange- XB
Black- Xb
If B allele is for orange fur and b allele for black fur,what are the genders phenotypes are the of the following:
XBY
XbY
XBXB
XbXb
XBXb
Orange
Black
Orange
Black
Orange or black because of the random X inactivation
In cats, the gene for coat color is located in the X chromosomes. One allele codes for orange coat (XB) and the other allele codes for black coat (Xb). A cross between an orange male cat and a calico female cat, would produce cats with _____ coat colors.
Orange and calico females and orange and black males
What are examples of human genetic disorders?
Cystic fibrosis, sickle cell, tay sactis, hemophilia
What is nondisjunction?
Failure of homologues and sister chromatids separate
What is aneuploidy?
Gain or loss of chromosomes
What happens to the gametes if no disjunction occurs at anaphase 1? What fails to separate in this case?
Homologous chromosomes
What happens to the gametes if no disjunction occurs at anaphase 2. What fails to separate in this case?
Sister chromatids
Separation of tetrads occurs when?
Anaphase 1
Particulate inheritance?
One or the other, not a blend of traits
Second law
Separate independently
Dihybrid cross
Only genes nonhomologous
Cock feathering is a _____ allele only.
Recessive
Why does X inactivation happen?
To prevent from doubling
X inactivation in _____ after fertilization.
Somatic cells
Nondisjunction can result to _____.
Down syndrome
