Chapter 21- Human development and genetics

Question 1

Define fertilization.

Answer 1

sperm fertilizes an ovum > cell undergoes capacitation, which involves acrosome enzymes that digest the layers of the cell and membrane around the ovum at fertilization. These changes inhibit entry for any other sperm => Meiotic cell division => zygote chromosomes become diploid again in the nucleolus

• typically occurs in the fallopian tube.
• mitotic divisions called cleavage
• • • ++ + divisions lead to solid sphere called morula, becomes hollow and is called a blastocyst. outer layer full of fluid is called trophoblast and the inner cell mass (ambryoblast) contains potential embryo.
• • Note blastocyst state becomes implanted to uterine wall 5-8 days after fertilization. If successful the trophoblast becomes the chorion.

Question 2

how many pairs of chromosomes are there in a human cell?

Answer 2

22 pairs of autosomes
1 pair of sex chromosomes (X, Y)
total 46 chromosomes, 23 homologous pairs .

Question 3

What are fraternal twins?

Answer 3

results of two separate ova fertilized by separate sperm

Question 4

What are identical twins?

Answer 4

result of splitting of the very early embryo before the cells start to specialist. this results in to identical sets of embryos
conjoined twins is when the embryo remains partly fused.

Question 5

what is an embryo

Answer 5

the developing human individual from the time of fertilization until the eight week of gestation.

Question 6

what is amnion?

Answer 6

thin membrane that eventually surrounds the embryo and contains amniotic fluid, which provides cushion for the fetus against mechanical injury.

Question 7

what structures are derived from the primary germ layer known as ectoderm

Answer 7

• epidermis; hair and nail follicles; sweat glands
• nervous system; pituitary gland; adrenal medulla
• lens and cornea; internal ear
• mucosa of oral and nasal cavities; salivary glands

Question 8

what structures are derived from the primary germ layer known as mesoderm

Answer 8

• dermis; bone and cartilage
• skeletal muscles, cardiac muscles, mot smooth muscles
• kidney and adrenal cortex
• bone marrow and blood; lymphatic tissue; lining of blood vessels.

Question 9

what structures are derived from the primary germ layer known as endoderm

Answer 9

• mucous of esophagus, stomach and intestines
• epithelium of respiratory tract, lungs
• liver and mucosa of gallbladder
• thyroid gland, pancreas

Question 10

what tests are available to determine certain kinds of abnormalities in a fetus or to monitor development

Answer 10

1. ultrasound-
2. amniocentesis- chromosome investigations
3. chorionic villus sampling (CVS) - as above, but can be done earlier
4. maternal blood test: AFP if elevated after 16 weeks, 95% change of spina bifida or other malformation

Question 11

What changes are expected to happend during pregnancy in relation to 
1. weight 
2. uterus
3. thyroid gland
4. skin
5. circultory system
6. digestoive system
7. urinary system
8. respiratory system
9, skelatal sytstem

Answer 11

1. 2-3lbs per month
2. enlarges and moves abdo organs up
3. ^ [thyroxine] which ^ metabolic rate
4. stretch marks
5. HR increases, stroke volume and cardiac output; blood volume increases, varicose veins
6. nausea and vomiting, constipation
7. kidney activity increases, + urgency,
8. resp rate increase, lung capacity decreases,
9. lordosis may occur, sacroiliac joints and pubic symphysis become more flexible.

Question 12

describe the placenta and its two functions.

Answer 12

made of both detal and maternal tissue.
formed in 3rd month of gestation
-blood of fetus and mother tend to be separate.
2 functions: to be the site of exchange between maternal and fetal blood and to produce hormones to maintain pregnancy.

Question 13

What connects the fetus to the placenta?

Answer 13

umbilical cord: which is two umbilical arteries that carry blood from the fetus to the placenta and one umbilical vein that returns blood from the placenta to the fetus.

Question 14

What is teratogen in terms of congenital fetal infections?

Answer 14

anything that may cause developmental abnormalities in an embryo-fetus

Question 15

what is congenital rubella syndrome?

Answer 15

virus of german measles. consequences of mother being infected results in possible stillbirth, heart defects deafness or mental retardations.

Question 16

what is congenital varicella syndrome?

Answer 16

chickenpox during pregnancy- may cross the placenta and result in malformed limbs, scars, blindness and mental retardation

Question 17

What is congenital syphilis?

Answer 17

STI bacteria that can cross the placenta after the 4th month of gestation. can result in death, malformations or cataracts. Child can be born with syphilis

Question 18

what is Fetal alcohol syndrome?

Answer 18

group of characteristics present in infants who were exposed to alcohol during fetal stages. This can cause low birth weight, small head, heart defects, malformation and behaviour issues.

Question 19

what is after birth?

Answer 19

when the baby is delivered, the umbilical cord is cut. The placenta then detaches from the uterine wall and is delivered with the rest of the umbilical cord.

Question 20

What hormones are secreted by the placenta?

Answer 20

1. human chorionic gonadotropin (hCG) - first and stimulates corpus luteum to secrete estrogen and progesterone.
2. Estrogen and Progesterone: which inhibits the anterior pituitary secretion of FSH and LH, so no other follicles develop. Also prepare mammary glands for lactation
3. Relaxin: inhibits contractions fo the myometrium, permits stretching of the ligaments of the pubic symphysis so that the joints give at birth.

Question 21

what is Parturition and labor?

Answer 21

Parturition: birth
labor: sequence of events that occur during birth

Question 22

Labour may be divided into 3 stages. Briefly describe each

Answer 22

1. dilation of cervix then amniotic sac breaking.
2. delivery of infant- contracts brought on by oxytocin. if head is not in right direction its called a breech and C-section may be required.
3. delivery of the placenta (after birth) - continued contractions expel the placenta and membranes. The endometrium closes the ruptured blood cells to prevent sever hemorrhage.

Question 23

What happens to the baby’s body in response to breathing?

Answer 23

^ pulmonary circulation
^ blood going to Lt atrium which closes flap fo the foramen ovale,
ductus arteriosus begins to constrict
ductus venosus begins to constrict and becomes a nonfunctional ligament in 1-2 weeks.

Question 24

Define 
1, genetics, 
2. genome 
3. gene
4. genotype
5. phenotype
6. dominant trait
7. recessive trait

Answer 24

1. study of inheritance.
2. complete genetic map
3. DNA code for one protein
4. actual genetic makeup that alleles present
5. appearance or how alleles are expressed
6. one allele takes over the over recessive allele
7. one allele that is taken over by a dominant allele

Question 25

each gene pair has two or move versions, which results in possibilities for expression. What do you call these possibilities?

Answer 25

alleles.

Each person has 2 alleles for each protein or trait.

Question 26

What do you call 2 alleles that are the same?

what do you call 2 alleles that are different?

Answer 26

homozygous for the trait

heterozygous for the trait

Question 27

what is the purpose of a punnet square?

Answer 27

show possible combinations of genes in the egg and sperm for a particular set of parents and the possible combinations or out comes.

Question 28

Describe the pattern of inheritance for Sickle-Cell anemia

Answer 28

most common genetic disease- Africa.
Recessive.
sickle-cell hemoglobin forms rigid crystals that distort and disrupt RBCs causing oxygen carrying capacity of the blood to be diminished

Question 29

describe the patter of inheritance of Cystic Fibrosis

Answer 29

most common genetic disease- Europe.
Recessive.
production of thick mucus clogs the bronchial tree and pancreatic ducts.
more severe forms effects are chronic resp infections and pulmonary failure

Question 30

describe the patter of inheritance of Tar-Sachs disease

Answer 30

most common (now rare) genetic disease- Jewish. Recessive.
Degeration of neurons and the nervous system results in death by the age of 2

Question 31

describe the patter of inheritence of Phenylhetonuria

Answer 31

Recessive.
lack of an enzyme to metabolize the amino acid phenylalanie which leads to severe mental and physical retardation.
These effects may be prevented by diet modifications during prenatal phase.

Question 32

describe the patter of inheritance of Huntington disease

Answer 32

dominant.
Uncontrolled muscle contractions begin between the ages of 30-50 years.
no tx

Question 33

describe the patter of inheritance of hemophilia

Answer 33

X-linked.

lack of fact 8 impairs chemical clotting; may be controlled with Factor 8 from donated blood.

Question 34

describe the patter of inheritance of duchennes’ muscular dystrophy

Answer 34

(x-linked) .
replacement of muscle by adipose/scar tissue with progressive loss of muscle function; often fatal before age 20 years due to involvement of cardiac muscle

Question 35

What is a sex-linked trait

Answer 35

the genes for the phenotype are located only on the X chromosome. These genes are recessive, but theres no corresponding genes on Y chromosome to mask them, and therefore men only have one X gene expression and usually express the phenotype.