Karyotypes and Mistakes in Meiosis

Question 1

Karyotypes

Answer 1

Images of homologous chromosomes - during cell division (mitosis), chromosomes can be stained, viewed and photographed; scientists can then count and arrange the chromosomes by size (helps them view abnormalities)

Question 2

Gametogenesis

Answer 2

The production of gametes
Sperm = spermatogenesis, Eggs = oogenesis
(With oogenesis, only one of the four cells receives enough cytoplasm, the rest are polar bodies and die)

Question 3

Sex Chromosomes and Sex Determination

Answer 3

Most species have at least one pair of chromosomes that differs between males and females - sex chromosomes (non sex chromosomes = autosomes)
In human males, one chromosome is much smaller than the other

Question 4

X and Y Chromosomes

Answer 4

Homologous pair that undergo synapsis, but not crossing over
Large chromosome = X and Small chromosome = Y
XX = Female and XY = Male

Question 5

Genetic Variability

Answer 5

1. Crossing Over: during prophase I, genes are swapped between homologous chromosomes (new combination of genes)
2. Random Assortment of Chromosomes: during metaphase I, homologous chromosomes line up randomly (some gametes receive all maternal, all paternal, or a mix of chromosomes)
3. Fertilization: which sperm fertilizes which egg is entirely random

Question 6

Non Disjunction

Answer 6

The failure of homologous chromosomes to move to opposite poles of the cell during meiosis, resulting in an abnormal number of chromosomes in the daughter cells (monosomy and trisomy)

Question 7

Monosomy

Answer 7

A chromosomal abnormality is which there is a single chromosome in place of a homologous pair

Question 8

Trisomy

Answer 8

A chromosomal abnormality in which there are three homologous chromosomes in place of a homologous pair

Question 9

Non Disjunction in Different Stages of Meiosis

Answer 9

Non disjunction in Meiosis I: all gametes have genetic abnormalities (2 that lack a chromosome and 2 that have two copies of a chromosome)
Non disjunction in Meiosis II: not as big of an effect (1 that lacks a chromosome, 1 that has two copies of a chromosome, 2 normal gametes)

Question 10

Down Syndrome

Answer 10

Trisomy of chromosome 21

Question 11

Turner Syndrome

Answer 11

One X and no Y sex chromosomes

Question 12

Klinefelter Syndrome

Answer 12

Two X and one Y sex chromosomes

Question 13

Patau Syndrome

Answer 13

Trisomy of chromosome 13

Question 14

Edwards Syndrome

Answer 14

Trisomy of chromosome 18

Question 15

Prenatal Testing

Answer 15

Testing for a genetic disorder that occurs prior to birth by collecting and observing fetal cells by (cells are used to make karyotype chart):
- CVS (Chorionic villus sampling)
- Amniocentesis

Question 16

CVS (Chorionic Villus Sampling)

Answer 16

Removing cells from the outer layer of membrane surrounding the embryo

Question 17

Amniocentesis

Answer 17

A long syringe is used to remove amniotic fluid to remove fetal cells

Question 18

In Vitro Fertilization

Answer 18

Eggs are retrieved from a female and fertilized outside of body, resulting embryo is placed in uterus of female

Question 19

Artificial Insemination (AI)

Answer 19

Placement of sperm directly in the reproductive tract of a female (uterus) –> sperm is “washed” to concentrate it