Lesson 4: Abnormalities in Sexual Reproduction

Question 1

what is our (humans) sex chromosomes like? how does each sex differ

Answer 1

• males have X and Y chromosome
• females have a pair of X chromosomes

Question 2

what are non-sex chromosomes called

Answer 2

autosomes

Question 3

what are some ways sex can be determined?

Answer 3

1. xx/xy (mammals, some insects)
2. zz/zw (birds)
3. temperature (crocodiles, turtles; if the eggs are kept relatively warm, most or all eggs hatch as females- if the eggs are kept relatively cool, most or all eggs hatch as males
4. age (some fish, some mollusks; all young are born as male- as they become older and larger, they change into females
5. social structure (some fish; all young fish are females, when the dominant male fish dies, a large female changes into a male
6. fertilization (haploid and diploid): bees, wasps, ants; fertilized eggs (2n) becomes females and unfertilized eggs (n) becomes males
7. infection (some insects; variable- in one form, infected individuals develop into females)
8. none (earthworms and other hermaphroditic organisms; all individuals have both female and male reproductive organs)

Question 4

what are some factors that can impact meiosis and fertilization (sexual reproduction)

Answer 4

several, including:
- these factors would be random meiotic errors
- environmental factors

Question 5

what are some ways meiosis can become abnormal?

Answer 5

chromosome seperation during anaphase 1 or 2 of meiosis 1 or 2

Question 6

what does abnormal meiosis seperation do? what does it result in? what is the name of THIS

Answer 6

results in one daughter cell having an extra chromosome and one daughter cell having a missing chromosome; known as non-disjunction

Question 7

example/explain non-disjunction in humans

Answer 7

results in gametes with 22 or 24 chromosomes, not the expected 23; this means that the resulting zygote would have 45 or 47 chromosomes, not the expected 46 (after fertilization)

Question 8

karyotype (how does it work and what is it)

Answer 8

non-disjunction can be easily observed through the use of a karyotype- it is a picture of chromosomes that have been arranged according to number, size, shape, and other characteristics
- it takes a snapshot of the chromosomes in the cell and you can identify any errors
- during cell division, chromosomes can be stated and photographed so they can be counted and compared

Question 9

types of non disjunction

Answer 9

1. trisomy: a chromosomial abnormality in which there are 3 homologous chromosomes in place of a homologous pair (when theres an extra chromosome)
2. monosomy: a chromosomal abnormality in which there is a single chromosome in place of a homologous pair (when theres a missing chromosome)

Question 10

non-disjunction disorders (what is it and what is an example of it)

Answer 10

many human genetic conditions are a result of non-disjunction
- down syndrome is an example

Question 11

down syndrome (whats it caused by, symptoms..)

Answer 11

caused by trisomy 21, or having 3 copies of the 21st chromosome
- the extra chromosome means theres an excess of genetic information
- symptoms: round full face, short statue, intellectual disabilities, poor immune function, etc.

Question 12

turner syndrome

Answer 12

• one X and no Y sex chromosome
• approximately one in 2500 female births
• female in appearance but do not mature sexually and are sterile
• most turner syndrome fetuses are miscarried before the 20th week of pregnancy

Question 13

Klinefelter syndrome

Answer 13

• two X and one Y sex chromosome
• approximately one in 500 male births
• males are usually sterile and exhibit some feminine body characteristics, but severity varies

Question 14

patau syndrome

Answer 14

• trisomy of chromosome 13
• approximately one in 25000 live births
• many serious developmental problems including brain, kidney, and heart defects
• children rarely live more than a few months

Question 15

edwards syndrome

Answer 15

• trisomy of chromosome 18
• approximately one in 6000 live births
• many organ system defects
• very low survival rate
• most fetuses die before birth
• average life expectancy of live-born infants is less than one month

Question 16

how do genetic disorders get diagnosed prior to birth?

Answer 16

pre-natal testing

Question 17

how does pre-natal testing work at 8 weeks? (what are the different processes/procedures for this)

Answer 17

you can collect fetal cells
- chorionic villus sampling (CVS) removes cells from placenta for testing
- amniocentesis involves the use of a syringe to collect cells from the amniotic sac for testing

Question 18

how does pre-natal testing work at 15-20 weeks?

Answer 18

you can do multiple marking screening
- this accesses hormone levels in the mothers blood to check for markers of increased risk of genetic conditions

Question 19

what are some causes of problems with fertilization

Answer 19

• poor or reduced egg and sperm quality or quantity
• blocked fallopian tube of the female
• blocked epididymis or vas deferens of the male

Question 20

what are assistive reproductive technologies (ARTs) used for?

Answer 20

can be used to increase reproductive success

Question 21

ARTS: In Vitro Fertilization (IVF) what is the process like?

Answer 21

• 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 22

Assistive Reproductive Technologies: Artificial insemination (what is this process like and what is this technique used for)

Answer 22

• 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 then inserted directly into the uterus
• this technique has also been used in non-humans to help save endangered species, including pandas