Development and Heredity Overview

These flashcards cover topics related to the processes of development and heredity as outlined in the lecture notes.

What marks the beginning of prenatal development?

Fertilization.

What is the duration of prenatal development?

38 weeks after conception (266 days).

List the three periods of prenatal development.

Preembryonic, embryonic, & fetal periods.

What occurs during capacitation of sperm?

The membrane around the tip of the sperm's head is weakened to release enzymes.

Where does fertilization occur?

In the fallopian tube.

What is a zygote?

The single cell formed from the union of sperm and egg, containing 46 chromosomes.

How long is the ovum viable after release?

About 24 hours.

How long are sperm fertile in the female reproductive tract?

About 2-3 days.

What is the blastocyst?

A hollow sphere of cells ready for implantation, formed by day 5 after fertilization.

What hormone is secreted by the blastocyst during implantation?

Human chorionic gonadotropin (hCG).

What is the function of hCG during early pregnancy?

It maintains the secretion of progesterone from the corpus luteum.

What are the three primary germ layers developed from the blastocyst?

Ectoderm, mesoderm, and endoderm.

What is formed from the endometrium and the chorion?

The placenta.

What are the functions of the placenta?

Nutritive, respiratory, and excretory role for the embryo/fetus.

What are the umbilical structures and their roles?

Two arteries and one vein connecting the fetus to the placenta.

What period marks the critical development for organ systems?

Embryonic development, from the beginning of the 3rd week to the end of the 8th week.

What is the estimated size of the embryo by the end of the embryonic period?

1 inch (2.5 cm) long.

What is defined as the period of growth and maturation for the fetus?

Fetal development, beginning from the 9th week until birth.

At what week can sex be determined in fetal development?

By the end of the 16th week.

What is vernix caseosa?

The cheese-like material covering the skin of the fetus.

What defines the three trimesters of pregnancy?

Commonly divided into 3 trimesters over 40 weeks.

What is the term for a baby born before 37 weeks?

Premature.

What are genes?

Segments of DNA on chromosomes that carry codes for specific traits.

What is the function of meiosis in reproduction?

It reduces chromosome number to 23 in gametes.

What are the types of chromosomes and their pairs?

1 pair of sex chromosomes and 22 pairs of autosomes.

Explain dominant and recessive traits.

Dominant traits mask recessive traits; recessive traits manifest if both alleles are recessive.

What is a genotype?

The genetic makeup of a person for a trait.

What is a phenotype?

The physical expression of the genotype.

What genotype produces brown eyes?

BB or Bb, with B being the dominant allele.

What is a carrier of a genetic trait?

A person with a heterozygous genotype who can transmit the gene without expressing it.

What are the possible genotypes for blood type A?

AA or AO.

What is the difference between X and Y chromosomes?

X is larger and contains more genes; Y determines male characteristics.

How are sex-linked traits inherited?

X-linked traits are expressed differently in males and females due to the lack of a second X in males.

What is genetic mutation?

A change in an individual’s genetic code that can be inherited if it occurs in reproductive cells.

What contributes to genetic variation during gamete formation?

Independent assortment of chromosomes, crossover of homologues, and random fertilization.

Define segregation in meiosis.

The separation of two alleles of one particular trait into different daughter cells.

Define independent assortment in meiosis.

The distribution of alleles of different traits independently of each other.

How are traits inherited through independent assortment?

Different combinations of traits can be inherited, creating genetic diversity.

What is the significance of random fertilization?

It further increases genetic variation among offspring.