Genetics: Meiosis Quiz

Since the cell we are discussing originally had 4 chromosomes each of the offspring cells now has ___________ as many chromosomes as before.

1/2

Since the number of chromosomes in the cells has been reduced during the first meiotic division (meiosis 1), the first division is sometimes called the REDUCTIONAL division. The number of chromosomes has been reduced by ____________.

1/2

A cell which has only one of each pair of homologous chromosomes present is in the haploid condition. A haploid cell has ______ as many chromosomes as a diploid cell.

1/2 (half)

If the number of chromosomes in a diploid cell of an organism is 20, the number of chromosomes in a haploid cell is __________.

10

Each group of 4 chromatids is called a TETRAD. How many tetrads are present ?

2

Each pair of chromatids connected by the centromere can still be called a "chromosome". At the end of meiosis 1 each offspring cell contains _________ chromosomes.

2

In each tetrad, which pair of chromatids goes to which pole is purely a matter of chance. This results in INDEPENDENT ASSORTMENT, because the way in which genetic information contained in one tetrad is distributed is independent of the way in which the information in other tetrads is distributed. At the end of Meiosis 1 each offspring cell contains _________ pairs of chromatids.

2

In the following discussion assume cells containing four chromosomes in the diploid condition. This means that there are________ homologous pairs present.

2

One chromatid (now a chromosome) from each pair moves to each pole during anaphase 2. At the end of meiosis, each daughter cell has _________ chromosomes?

2

Since the chromatids are no longer paired, we can now call each one a chromosome. At the end of Meiosis each offspring cell has ______ chromosomes.

2

during metaphase 1 the tetrads line up along the equatorial plate. The centromeres still hold pairs of chromatids together. During anaphase 1 the tetrads splits and one pair goes to each pole. The centromeres still hold each pair together. How many chromatids go to each pole?

2

Because they have only half the normal chromosomes, the offspring cells are said to be HAPLOID. If the diploid number of chromosomes in the original cells had been 46, what would the haploid number be ?

23

During prophase 1 SYNAPSIS occurs. During synapsis homologous chromosomes are attracted to each other, and move until they are side by side. This results in groups of ___________ homologous chromatids.

4

Each chromosome moves to the equatorial plate in metaphase 2, and the centromeres split. There are now___________ individual chromosomes (formerly chromatids)

4

The centromere, a structure located on the chromosome, does not split during replication. This means that the two identical chromatids that now make up each chromosome are connected by the centromere. There are now __________ pairs of chromatids in the cell? (Assume 4 original chromosomes, as in question 19)

4

Space limitations in the nucleus preclude a doubling of the chromosome number with each generation. Instead there is a process called meiosis by which the number of chromosomes in the gametes is reduced to half that of the cells of the parents. If a gamete contains 23 chromosomes, the cells of the parent contain___________.

46

Sometimes during interphase the chromosomes replicate. This means that they split down the middle and duplicate themselves exactly. Each chromosome is now made up of two parts, each called a chromatid. If there were 4 chromosomes originally, there are now ___________ chromatids.

8

There are now __________ chromatids in the cell.

8

Since the two chromatids of each pair were identical except for the effects of crossing over, the two offspring are a) homologous b) almost identical c) similar

almost identical

At the beginning of prophase 2 the cell contains 2 chromosomes, each made up of 2 chromatids. The two chromatids that make up each chromosome are held together by the __________.

centromere

The chromatids in each pair are connected by the ___________.

centromere

After meiosis 1 ends, meiosis 2 begins in each of the two offspring cells produced by meiosis 1. There is NO replication between meiosis 1 and meiosis 2. What is "replication"?

exact duplication of chromosomes

Meiosis is the process by which a diploid cell becomes a haploid cell. When ____________ takes place, two haploid cells fuse to form a diploid cell.

fertilization

During sexual reproduction the two parental organisms each produce a gamete. These two gametes fuse to form a zygote. The zygote then divides by mitosis to form new organisms. Sperms and eggs are___________.

gametes

Obviously meiosis must proceed so that the zygote receives all the needed information. This is possible because chromosomes come in pairs. The two members of each pair are said to be homologous because their origins are the same; consequently, they have the same size and shape, and carry information concerning the same things. Meiosis is a process that _____________ the chromosome number.

halves

A cell in which the chromosomes are found in pairs is said to be in the diploid condition. The two chromosomes in each pair are_______.

homologous

All of the chromatids in a tetrad are a) homologous b) identical c) different

homologous

Immediately after synapsis, when the homologous chromatids are very close to each other, they may exchange pieces of themselves with each other. This is called crossing over. Crossing over takes place between ______________ chromosomes.

homologous

SYNAPSIS occurs when____________ chromosomes move together.

homologous

The two chromatids that made up each chromosome are a) similar b) identical c) different

identical

A diploid cell is a cell which the chromosomes appear a) in homologous pairs b) in analogous c) as single units

in homologous pairs

If one chromosome of a homologous pair carries information for blue eyes at a certain point, the other chromosome of the pair must carry at a comparable point a) information for blue eyes b) information of eye color c) information for brown eyes

information for eye color

When a cell is not dividing, it is in interphase. Most cells in an organism are not dividing and therefore in _____________.

interphase

Does replication take place between Meiosis 1 and meiosis 2 ?

no

Note that although the haploid condition has only half as many chromosomes at the diploid, the fact that one of each pair of homologous chromosomes is present means that there is still information present for each trait. In the diploid condition there are two pieces of information for each trait. In the haploid condition there is __________ piece(s) of information for each trait.

one

Meiosis consisted of two cell divisions, called meiosis 1 and meiosis 2. These cell divisions are similar to mitosis, and each is divided into the same four stages. These stages or phases are ______, ______,______, and ______.

prophase metaphase anaphase telophase

As a result of crossing over a particular chromosome will still carry information about the same things, e.g., hair color or skin pigment. It may, however, carry a different combination of information. As a result of crossing over, genetic information is a) lost b) rearranged c) gained d) changed

rearranged

Homologous Chromosomes are a) identical b) similar c)different

similar

A haploid cell is one in which a) there are 1/2 as many chromosomes as in the gamete b) the chromosomes are 1/2 as big c) there is only one chromosome present from each homologous pair

there is only one chromosome present from each pair

Meiosis is the process that halves the chromosome number. This halving is not however completely random; if it were the offspring might lack essential information. For example, a particular chromosome might contain information relating to the structure of the kidneys. If by chance, neither gamete which made up the offspring contained this chromosome, the organism would not be able to build kidneys. True/false

true

homologous chromosomes carry information about the same things, but the information is not necessarily the same. For example, if one chromosome of a particular pair carries information about hair color at a certain location, the other member of the pair will also have information about brown hair color at a comparable location. However, one might carry a gene for brown hair, and the other for blond. True/ false

true

If each gamete had the same number of chromosomes as the parent organism, the zygote formed by the union of the two gametes would have________________ chromosomes. (a) half as many (b) the same number as (c) twice as many

twice as many