Two of the embryos will be trisomic for chromosome 18, and two will contain a single copy of chromosome 18.
In theory, when a nondisjunction for chromosome 18 occurs during meiosis I, four gametes can be produced. If these gametes are fertilized with unaffected gametes from the second parent, what observations would you make concerning the resulting embryos?
Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried.
Although in humans there are 22 pairs of autosomal chromosomes, only three different chromosomal trisomies are commonly seen in newborns. Of the remaining 19 autosomes, many trisomies have not been seen in newborns. Why not?
can reveal alterations in chromosome number.
Karyotyping
During mitosis, chromosomes are more condensed than during interphase.
Scientists commonly choose white blood cells that are going through mitosis to prepare karyotypes. Why?
homologous or non-sister chromatids
At a chiasma, two ________ are attached to each other.
This brings the chromosomes into alignment so that crossing over can create new combinations of genes present on a single chromosome.
During meiosis I, homologous chromosomes form a tetrad. What does this accomplish?
Genetic diversity is enhanced by mitosis.
Which of the following statements regarding genetic diversity is false?
two
In a cell with eight chromosomes, one chiasma develops during meiosis I in only one particular pair of homologs. How many recombinant chromosomes will there be at the completion of meiosis II?
shuffling cards and dealing out hands of poker
Independent orientation of chromosomes at metaphase I and random fertilization are most like
possible combinations of characteristics
Independent orientation of chromosomes at metaphase I results in an increase in the number of
64
If we assume that crossing over does not occur, how many different combinations of chromosomes are possible in a zygote derived from diploid parents who each have three pairs of chromosomes?
Meiosis provides for asexual reproduction.
Which of the following statements regarding mitosis and meiosis is false?
Crossing over is a phenomenon that creates genetic diversity during mitosis.
Which of the following statements regarding the differences between mitosis and meiosis is false?
determine an individual’s sex
sex chromosomes-
the remaining 22 pairs of chromosomes in both males and females
autosomes-
a cell containing two homologous sets of chromosomes
diploid-
a sex cell, haploid egg or sperm
gamete-
a cell containing a single set of chromosomes
haploid-
a fertilized egg
zygote-
sets of four chromatids
tetrads-
an exchange of corresponding. segments between nonsister chromatids and homologous chromosomes
crossing over-
the sites of crossing over
chiasma-
an ordered display of an individual’s chromosomes in pairs
karyotype-
also known as Down syndrome
trisomy 21-
when members of a chromosome pair fail to seperate
nondisjunction-
a typical body cell which has 46 chromosomes
somatic cell-
two chromosomes in a matching pair
homologous chromosomes-
the site where a gene is found on a chromosome
locus-
