Abnormalities in Sexual Reproduction (lesson four)

Question 1

Sex Determination

Answer 1

• Males have an X and a Y chromosome
• Females have a pair of X chromosomes
• All non-sex chromosomes (#s 1-22) are called autosomes

Question 2

Factors Affecting Sexual Reproduction

Answer 2

• Several factors can impact these two processes
• Some of these factors would be random meiotic errors
• Others would be environmental factors

Question 3

is it possible for an entire chromosome to be added or lost?

Answer 3

It is possible that an entire chromosome can be lost or gained by cells if the homologous chromosomes fail to separate in anaphase I or II of meiosis I or II

Question 4

what would a chromosome being lost or added cause?

Answer 4

• This would result in one daughter cell having an extra chromosome and the other having a missing chromosome
• This is called non-disjunction

Question 5

Abnormal Meiosis (non-disjunction)

Answer 5

• In humans, this would result in gametes with 24 and 22 chromosomes, not the expected 23
• This also means that the resulting zygote would have 47 or 45 chromosomes, not the expected 46, after fertilization

Question 6

Can non-disjunction be observed and with what tool?

Answer 6

Nondisjunction can be easily observed through the use of a karyotype

Question 7

karyotype

Answer 7

• Your sex chromosomes can be viewed in a karyotype, and these are a pair of chromosomes that differ between males and females
• During stages of cell division, chromosomes can be stained and photographed so they can be counted and compared
• A picture of chromosomes that have been arranged according to number, size, shape, or some other characteristic is called a karyotype

Question 8

Types of Non-Disjunction

Answer 8

• Trisomy
• Monosomy

Question 9

Trisomy

Answer 9

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

Question 10

Monosomy

Answer 10

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

Question 11

what is Down syndrome caused by?

Answer 11

Down syndrome is caused by trisomy 21, or having 3 copies of the 21st chromosome
- This extra chromosome means there is an excess of genetic information
- Symptoms of this disorder include a round full face, short stature, intellectual disabilities, poor immune function, etc.

Question 12

pre-natal testing

Answer 12

In addition to karyotyping, genetic disorders can commonly be diagnosed before birth by pre-natal testing
- At 8 weeks, you can collect fetal cells
- Chorionic villus sampling (CVS) removes cells from the placenta for testing
- Amniocentesis involves the use of a syringe to collect cells from the amniotic sac for testing

Question 13

Diagnosing Non-Disjunction Disorders

Answer 13

• At 15-20 weeks, you can also do multiple marking screening
• This assesses hormone levels in the mother’s blood to check for markers of increased risk of genetic conditions

Question 14

Causes of Problems with Fertilization

Answer 14

Causes could include:
- Poor or reduced egg or sperm quality or quantity
- Blocked fallopian tube of the female
- Blocked epididymis or vas deferens of the male

Question 15

Assistive Reproductive Technologies (ARTs)

Answer 15

Assistive Reproductive technologies (ARTs) can be used to increase reproductive success

Question 16

In Vitro Fertilization (IVF)

Answer 16

• Hormone treatments are given to the woman to increase egg production
• Those eggs are retrieved through a minor procedure
• Fertilization occurs outside the body using a sample from the male, and the embryo is then implanted in the uterus

Question 17

Artificial Insemination

Answer 17

• This is when sperm is placed into the reproductive tract of a female through a process called intrauterine insemination
• A sperm sample, which can be fresh or frozen, is washed and concentrated and inserted directly into the uterus
• This technique has also been used in non-humans to help save endangered species, including pandas