Ch 11. Science

What is meiosis?

​Meiosis is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information. These cells are our sex cells - sperm in males, eggs in females. ● During meiosis one cell? divides twice to form four daughter cells. ● These four daughter cells only have half the number of chromosomes? of the parent cell - they are haploid. ● Meiosis produces our sex cells or gametes? (eggs in females and sperm in males). Meiosis can be divided into nine stages. These are divided between the first time the cell divides (meiosis I) and the second time it divides (meiosis II):

What symbol represents the number of chromosomes in a gamete?

"N" represents the number of chromosomes in a gamete.

How many alleles for the height gene does a pea plant gamete have?

2 alleles

What happens to the F1 generation generation if a heterozygous tall pea plant is crossed with a homozygous short pea plant?

50% of the F1 generation will be (Tt) yields tall plants which and 50% will be (tt) which yields short plants.

What are gametes?

A Gamete is a mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote. Example- egg and sperm.

What are diploids?

A diploid cell is a cell that contains two sets of chromosomes. One set of chromosomes is donated from each parent. Examples: The diploid number of a cell is the number of chromosomes in the cell. This number is commonly abbreviated as 2n, where n stands for the number of chromosomes. For humans this equation would be 2n=46.

What is a hybrid?

A hybrid is a offspring of crosses between parents with different traits. T t T TT Tt T TT Tt

What are regulatory genes?

A regulatory gene is any gene that REGULATES control over the expression of another gene. A regulatory gene may "silence" another gene from expressing its dominant trait. For example the Manx cat has no tail bc it has a regulatory gene that silences the gene that expresses the tail. This tail silencing gene is dominant and has possible alleles S= silences tail gene= no tail (Manx cat). the s= doesn‛t silence tail gene= has tail (non-Manx cat).

What is a tetrad?

A tetrad is a structure containing 4 chromatids that form during meiosis.

Using the Punnett Square above, what can you tell about the offspring of this cross?

All have inherited the tall trait.

What are alleles

Alleles are different forms of a gene. They can be dominant or recessive.

Explain how allowing the generation F1 to self- pollinate in producing the F2 generation allowed Mendel to reach his conclusion about inheritance

Allowing the F1 pea plant to self pollinate caused the recessive phenotype to reappear in the F2 generation. Self-pollination of the F1 plants also allowed the 3:1 phenotype ratios to occur, supporting Mendel‛s theory. Self pollination showed that traits controlled by the recessive alleles could reappear in the F2 generation.

What are phenotypes?

An individual's phenotype consists of the traits we can observe. These can include features of appearance, behavior, metabolism, or anything else we can detect. Traits related to appearance are sometimes the easiest to observe Humans have appearance phenotypes, too; for example, your height and your eye color are both phenotypes controlled, at least partly, by your genes.

What are genotypes?

As the name suggests, a person's genotype refers to the types of genes he or she has for a particular inheritable trait. Genotypes determine which characteristics an individual will express, for example: whether they have freckles or not, if they are lactose intolerant, if they have hair on their knuckles or if their eyes will be blue, brown or another color.

If a pea plant‛s alleles for height are tt, what could be said about the parents?

Both carried the tt recessive allele. They both had heterogeneous alleles for height (Tt)

What is the difference between mitosis and meiosis?

Cells divide and reproduce in two ways: mitosis and meiosis. Mitosis is a process of cell division that results in two genetically identical daughter cells developing from a single parent cell. Meiosis, on the other hand, is the division of a germ cell (such as sperm and egg) involving two fissions of the nucleus and giving rise to four gametes, or sex cells, each possessing half the number of chromosomes of the original cell. Mitosis is used by single-celled organisms to reproduce; it is also used for the organic growth of tissues, fibers, and membranes. Meiosis is found in sexual reproduction of organisms. The male and female sex cells (i.e., egg and sperm) are the end result of meiosis; they combine to create new, genetically different offspring

What are chromatids?

Chromatids are 1 of 2 identical "sister" parts of a duplicated chromosome.

When do chromosomes form tetrads?

Chromosomes form Tetrads during meiosis in Prophase I.

What is codominance?

Codominance occurs when both phenotypes produced by both alleles are clearly expressed. Such as when a red flower crosses with a white flower and instead of having either white or red flowers the flowers are white with red spots.

Explain what is happening in this image.

Crossing over

What are daughter cells?

Daughter cells are cells that are produced as a part of the process of cell division. Depending on whether cells are dividing in mitosis or meiosis, the daughters can be genetically identical to the parent cell or they may be different.

Which principle explains why a female bison and male bison that are both heterozygous for normal skin pigmentation (Aa) produce an albino offspring (aa).

Dominance and segregation explain why the heterozygous (Aa) parents can have an albino offspring.

How are gametes produced?

Gametes are produced by a type of cell division called meiosis. They are haploid, meaning that they contain only one set of chromosomes. When the haploid male and female gametes unite in a process called fertilization, they form what is called a zygote. The zygote is diploid and contains two sets of chromosomes.

What is a gamete

Gametes are reproductive cells (sex cells) that unite during sexual reproduction to form a new cell called a zygote. Gametes are produced by a type of cell division called meiosis. They are haploid, meaning that they contain only one set of chromosomes.

What are gene maps?

Gene maps are a graphic representation of the order of genes within chromosomes by means of detailed analysis of the DNA. They are based on the frequencies of crossing over.

What are linked genes?

Genes that are inherited together with the other gene(s) as they are located on the same chromosome

What are haploids?

Haploid describes a cell that contains a single set of chromosomes. The term haploid can also refer to the number of chromosomes in egg or sperm cells, which are also called gametes. In humans, gametes are haploid cells that contain 23 chromosomes, each of which a one of a chromosome pair that exists in diplod cells. The number of chromosomes in a single set is represented as n, which is also called the haploid number. In humans, n = 23. Haploids contain HALF the number of chromosomes of a diploid. Thus, if an organism has a diploid number of 24 the haploid number is 12. ​

Why did Gregor Mendel remove the male parts of flowers of some plants?

He removed the male parts to control the crosses between plants.

What does heterozygous mean?

Heterozygous refers to having two different alleles for a single trait. Examples: The gene for seed shape in pea plants exists in two forms, one form or allele for round seed shape (R) and the other for wrinkled seed shape (r). A heterozygous plant would contain the following alleles for seed shape: (Rr).

What does homozygous mean?

Homozygous refers to having identical alleles for a single trait. An allele is a form of a gene. Example: The gene for seed shape in pea plants exists in two forms, one form or allele for round seed shape (R) and the other for wrinkled seed shape (r). The round seed shape is dominant and the wrinkled seed shape is recessive. A homozygous plant would contain the following alleles for seed shape: (RR) or (rr). The (RR) genotype is homozygous dominant and the (rr) genotype is homozygous recessive for seed shape.

Explain why Thomas Hunt Morgan used fruit flies in his studies.

Hunt Morgan used fruit flies in his experiment bc fruit flies produce large numbers of offspring.

Explain how a trait might seem to "disappear" for a generation, and then "reappear" in the following generation.

If all of the individuals in a generation receive one dominant allele and one recessive allele, then they would all show the dominant trait. If they are bred, then they will pass on the dominant allele to some of their offspring and the recessive allele to the others. Offspring receiving 2 recessive alleles will show the recessive trait, so it will reappear.

What happens if 2 genes are far apart on a chromosome?

If they are far apart, they are less likely to be inherited together

What is incomplete dominance?

Incomplete dominance is occurs when one allele is not completely dominant over the other allele. In incomplete dominance, the heterozygous phenotype lies somewhere between the 2 homozygous phenotypes. For example if you cross a red and white flower and the cross yields pink flowers.

What is independent assortment?

Independent assortment is a basic principle of genetics developed by a monk named Gregor Mendel in the 1860's. Mendel formulated this principle after discovering another principle now known as Mendel's law of segregation. This principle states that the ​alleles​for a trait separate when gametes are formed. These allele pairs are then randomly united at ​fertilization​. ​Mendel arrived at this conclusion by performing monohybrid crosses

How is meiosis I different from mitosis?

Meiosis I produces 2 haploid daughter cells, but mitosis produces 2 diploid daughter cells.

Why did Mendel choose pea plants to study genetics?

Mendel chose pea plants bc they can produce many offspring, they have traits that come only in 2 forms, and crosses between the plants can be controlled easily

What are multiple alleles?

Multiple alleles have more than 2 variations of a gene. An example of multiple alleles is human blood types. People can have A, B, AB or O blood types.

Looking at the Punnett Square above, what can be said about the relationship between pea shape and pea color?

Pea shape and pea color are independent of each other, they are assorted independently RY Ry RY Ry RY RRYY RRYy RRYY RRYy Ry RRYy RRyy RrYy RRyy rY RrYY RrYy RrYY RrYy ry RrYy Rryy RrYy Rryy

What are polygenic traits?

Polygenic traits are traits that are said to be dominated by 2 or more genes. Polygenic traits often show a wide range of phenotypes. The variety of skin color in humans comes about partially bc more than 4 different genes control this trait

What is the P generation?

The "p" stands for parental. Parental generation is the first generation involving two individuals that are mated to foresee or analyze the genotypes of their offspring.

What happened to the F1 generation when Gregor Mendel crossed a tall pea plant with a short plant?

The F1 generation inherited one allele from each parent.

What is the F1 generation?

The F1 generation is the first generation of offspring produced by a set of parents. The 'F' in F1 stands for 'filial.' So in short, F1 means 'first filial generation'.

What is the F2 generation?

The F2 generation is the result of a cross between two F1 individuals (from F1 generation).

Explain the principle of independent assortment?

The Principle of Independent Assortment describes how different genes independently separate from one another when reproductive cells develop. Independent assortment of genes and their corresponding traits was first observed by Gregor Mendel in 1865 during his studies of genetics in pea plants

Explain why short plants reappeared in the F2 generation if in the P generation, a tall plant was crossed with a short plant.

The allele for both heights segregated when the F1 plants made gametes.

What is the end result of meiosis?

The end result is haploid cells

A tall plant (TT) is crossed with a short plant (tt). If the tall F1 pea plants are allowed to self pollinate, the offspring what will happen?

The offspring could be tall or short. See explanation below: P generation (TT) and (tt) T T t Tt Tt t Tt Tt 100% of offspring will be tall. Fi generation being allowed to self pollinate (Tt) and (Tt) T t T TT Tt t Tt tt 75% will be tall and 25 % will be short

How can the principles of probability be used?

The principle of probability can be used to predict the traits of offspring of genetic crosses.

What is the principle of segregation?

The principle of segregation states that during gamete formation, the alleles for each gene segregate from each other, so that each gamete carries only one allele for each gene. RY Ry rY ry RY RRYY RRYy RrYY RrYy Ry RRYy RRyy RrYy Rryy rY RrYY RrYy rrYY rrYy ry RrYy Rryy rrYy rryy Seed Shape-​R= Round, r= Wrinkled See Color-​Y= Yellow, y= green

Use the Punnett square above to answer this question. If a pea plant that is heterozygous for round, yellow peas (RrYy) is crossed with a pea plant that is homozygous for round peas but is heterozygous for yellow peas (RRYy), how many different PHENOTYPES are their offspring expected to show?

There will only be 2 phenotypes bc all are going to be round (they are all RR or Rr which yields round shape) There is no rr which yield wrinkled shape. The only variant will be if they are yellow or green (YY and Yy yield yellow and yy yield green).

If a breed of chicken show codominance for feather color, one allele codes for black feathers and another for white feathers, what will the feathers of heterozygous chickens of this breed be?

They will be speckled bc of codominance. Neither the black or white dominates

What can you apply Mendel‛s principle of genetics to?

You can apply Mendel‛s principles to all organisms.

`What happens to 2 genes if they are on the same chromosome and rarely assort independently

You can infer that they are probably close together