Question

can you give me every single questions answers with reference.

1. What do the terms “genotype” and “phenotype” mean?

2. Briefly explain the three factors that contribute to genetic variability.
   1. Independent assortment
   2. Crossover of homologues
   3. Random fertilization

3. Briefly describe the following. Provide an example for each.
   1. Dominant-recessive inheritance
   2. Incomplete dominance inheritance
   3. Multiple-allele inheritance
   4. Sex-linked inheritance
   5. Polygene inheritance
   6. Extranuclear (mitochondrial) inheritance (not really a pattern

4. What role, if any, do environmental factors play in gene expression?

5. What is genetic screening? Why do they determine pedigrees?

6. Compare/contrast amniocentesis and chorionic villus sampling (including the benefits and risks associated with each).

Answer 1

1
Genotype, the genetic constitution of an organism. The genotype determines the hereditary potentials and limitations of an individual from embryonic formation through adulthood. Among organisms that reproduce sexually, an individual’s genotype comprises the entire complex of genes inherited from both parents
organism's genotype is the set of genes that it carries. An organism's phenotype is all of its observable characteristics — which are influenced both by its genotype and by the environment. .
term "phenotype" refers to the observable physical properties of an organism; these include the organism's appearance, development, and behavior.

a
The Principle of Independent Assortment describes how different genes independently separate from one another when reproductive cells develop.
law of independent assortment states that the alleles of two (or more) different genes get sorted into gametes independently of one another. In other words, the allele a gamete receives for one gene does not influence the allele received for another gene.
independent assortment of genes occurs during meiosis in eukaryotes. Meiosis is a type of cell division that reduces the number of chromosomes in a parent cell by half to produce four reproductive cells called gametes. In humans, diploid cells contain 46 chromosomes, with 23 chromosomes inherited from the mother and a second similar set of 23 chromosomes inherited from the father. Pairs of similar chromosomes are called homologous chromosomes. During meiosis, the pairs of homologous chromosome are divided in half to form haploid cells, and this separation, or assortment, of homologous chromosomes is random. This means that all of the maternal chromosomes will not be separated into one cell, while the all paternal chromosomes are separated into another. Instead, after meiosis occurs, each haploid cell contains a mixture of genes from the organism's mother and father.

Another feature of of independent assortment is recombination. Recombination occurs during meiosis and is a process that breaks and recombines pieces of DNA to produce new combinations of genes. Recombination scrambles pieces of maternal and paternal genes, which ensures that genes assort independently from one another.

b
Crossing over occurs between prophase I and metaphase I and is the process where two homologous non-sister chromatids pair up with each other and exchange different segments of genetic material to form two recombinant chromosome sister chromatids.which occurs in the pachytene stage of prophase I of meiosis during a process called synapsis. Synapsis begins before the synaptonemal complex develops and is not completed until near the end of prophase I. Crossover usually occurs when matching regions on matching chromosomes break and then reconnect to the other chromosome. It can also happen during mitotic division, which may result in loss of heterozygosity. Crossing over is essential for the normal segregation of chromosomes during meiosis.Crossing over also accounts for genetic variation, because due to the swapping of genetic material during crossing over, the chromatids held together by the centromere are no longer identical. So, when the chromosomes go on to meiosis II and separate, some of the daughter cells receive daughter chromosomes with recombined alleles. Due to this genetic recombination, the offspring have a different set of alleles and genes than their parents do.
result is an exchange of genes, called genetic recombination.thus it causes genetic variation

c
Random fertilization means that the collection of genes within one gamete (such as a sperm cell) do not give that gamete a lesser or better chance than any of the other sperm cells of fusing with an egg cell to produce a zygote. This does not really generate new variation within the species, but it does preserve the variation that is already there. It does this by giving every version of every gene a more fair shot of being passed on to the next generation. If random fertilization was not occurring, that is, if some gene versions had a better chance of fertilizing an egg than other gene versions, then that gene version would increase in frequency in the next generation, while the other gene versions would decrease in frequency, and eventually there would only be one gene version left. In other words, there would no longer be any variation left for that gene

Random fertilization refers to the fact that if two individuals mate, and each is capable of producing over 8million potential gametes, the random chance of any one sperm and egg coming together is a product of these two probabilities - some 70 trillion different combinations of chromosomes in a potential offspring

Together with random fertilization, more possibilities for genetic variation exist between any two people than the number of individuals alive today.
each human couple could produce a child with over 64 trillion unique chromosome combinations!
Essentially, when the homologous pairs of chromosomes line up during metaphase I and then are separated at anaphase I, there are (2^23) possible combinations of maternal and paternal chromosome
Thus It create genetic variation

2

a dominant and reccesive inheritance

Alleles can be either dominant or recessive
Dominant alleles show their effect even if the individual only has one copy of the allele (also known as being heterozygous). For example, the allele for brown eyes is dominant, therefore you only need one copy of the 'brown eye' allele to have brown eyes (although, with two copies you will still have brown eyes).
Recessive alleles only show their effect if the individual has two copies of the allele (also known as being homozygous?). For example, the allele for blue eyes is recessive, therefore to have blue eyes you need to have two copies of the 'blue eye' allele.
An individual with one dominant and one recessive allele for a gene will have the dominant phenotype. They are generally considered “carriers” of the recessive allele: the recessive allele is there, but the recessive phenotype is not.

b
Incomplete dominance is when a dominant allele, or form of a gene, does not completely mask the effects of a recessive allele, and the organism’s resulting physical appearance shows a blending of both alleles. It is also called semi-dominance or partial dominance. One example is shown in roses. The allele for red color is dominant over the allele for white color, but heterozygous roses, which have both alleles, are pink.
Pink snapdragons are a result of incomplete dominance. Cross-pollination between red snapdragons and white snapdragons result in pink when neither the white or the red alleles are dominant.

c
Multiple Alleles
Alleles are alternative forms of a gene, and they are responsible for differences in phenotypic expression of a given trait (e.g., brown eyes versus green eyes). A gene for which at least two alleles exist is said to be polymorphic. Instances in which a particular gene may exist in three or more allelic forms are known as multiple allele conditions. It is important to note that while multiple alleles occur and are maintained within a population, any individual possesses only two such alleles (at equivalent loci on homologous chromosomes).

Examples Of Multiple Alleles
Two human examples of multiple-allele genes are the gene of the ABO blood group system, and the human-leukocyte-associated antigen (HLA) genes.

d
particularly important category of genetic linkage has to do with the X and Y sex chromosomes. These not only carry the genes that determine male and female traits but also those for some other characteristics as well. Genes that are carried by either sex chromosome are said to be sex linked.

Men normally have an X and a Y combination of sex chromosomes, while women have two X's. Since only men inherit Y chromosomes, they are the only ones to inherit Y-linked traits. Men and women can get the X-linked ones since both inherit X chromosomes.
X-linked recessive traits that are not related to feminine body characteristics are primarily expressed in the observable characteristics, or phenotype click this icon to hear the preceding term pronounced, of men. This is due to the fact that men only have one X chromosome. Subsequently, genes on that chromosome not coding for gender are usually expressed in the male phenotype even if they are recessive since there are no corresponding genes on the Y chromosome in most cases. In women, a recessive allele on one X chromosome is often masked in their phenotype by a dominant normal allele on the other. This explains why women are frequently carriers of X-linked traits but more rarely have them expressed in their own phenotypes.
non-sex determining X-linked genes are responsible for abnormal conditions such as hemophilia pronounce word, Duchenne muscular dystrophy pronounce word, fragile-X syndrome pronounce word, some high blood pressure, congenital night blindness, G6PD deficiency, and the most common human genetic disorder, red-green color blindness
Y-linked inheritance: Inheritance of genes on the Y chromosome. Since only males normally have a Y chromosome, Y-linked genes can only be transmitted from father to son.

Y-linked inheritance is also called holandric inheritance
Hypertrichosis of the ears, webbed toes, and porcupine man are examples of Y-linked inheritance in humans.
Webbed toes condition is characterized by having web-like connection between second and third toes. Porcupine man is a condition when the skin thickens and gradually becomes darker, scaly, rough, and with bristle-like outgrowths. Since Y-linked inheritance involves the Y chromosome, Y-linked inheritance is passed on from father to son.

e
Polygenic Inheritance Definition
Polygenic inheritance, also known as quantitative inheritance, refers to a single inherited phenotypic trait that is controlled by two or more different genes.

In a system which differs from Mendelian Genetics, where monogenic traits are determined by the different alleles of a single gene, polygenetic traits may display a range of possible phenotypes, determined by a number of different genes and the interactions between them.
The traits that are determined by polygenic inheritance are not simply an effect of dominance and recessivity, and do not exhibit complete dominance as in Mendelian Genetics, where one allele dominates or masks another. Instead, polygenic traits exhibit incomplete dominance so the phenotype displayed in offspring is a mixture of the phenotypes displayed in the parents. Each of the genes that contributes to a polygenic trait, has an equal influence and each of the alleles has an additive effect on the phenotype outcome.
Polygenic inheritance should not be confused with the effects caused by multiple alleles. In the case of multiple alleles, a gene contains several different allele variants on the same locus of each chromosome
physical traits that are controlled by polygenic inheritance, such as hair color, height and skin color, as well as the non-visible traits such as blood pressure, intelligence, autism and longevity, occur on a continuous gradient, with many variations of quantifiable increments.

f

Extranuclear inheritance or cytoplasmic inheritance is the transmission of genes that occur outside the nucleus. It is found in most eukaryotes and is commonly known to occur in cytoplasmic organelles such as mitochondria and chloroplasts or from cellular parasites like viruses or bacteria.
some ways that mitochondrial and chloroplast DNA differ from the DNA found in the nucleus:
High copy number. A mitochondrion or chloroplast has multiple copies of its DNA, and a typical cell has many mitochondria (and, in the case of a plant cell, chloroplasts). As a result, cells usually have many copies – often thousands – of mitochondrial and chloroplast DNA.
Random segregation. Mitochondria and chloroplasts (and the genes they carry) are randomly distributed to daughter cells during mitosis and meiosis. When the cell divides, the organelles that happen to be on opposite sides of the cleavage furrow or cell plate will end up in different daughter cells
Single-parent inheritance. Non-nuclear DNA is often inherited uniparentally, menining that offspring get DNA only from the male or the female parent, not both
In humans, for example, children get mitochondrial DNA from their mother (but not their father).

Environmental factors such as diet, temperature, oxygen levels, humidity, light cycles, and the presence of mutagens can all impact which of an animal's genes are expressed, which ultimately affects the animal's phenotype.