Genetics: Key Concepts of Genes, Genotypes, and Chromosomes

Genes are the sequence of DNA that provides _______

instructions for making a polypeptide

Genotype are the genetic constitution for a ___

particular gene

Phenotypes are the expression of your ___

genes

Homologous chromosomes are a pair of chromosomes that are the same in ____

size and gene content, but one came from the ovum and the other from the sperm

Autosomes/autosomal chromosomes are ___

all of the chromosomes except for the X and Y

Sex chromosomes are ___

the X and Y chromosomes

Locus:

gene's specific location on a chromosome

Alleles:

different versions of a gene

Homozygous means ____

having two of the same alleles for a particular gene

Heterozygous means ____

having two different alleles for a particular gene

Polygenic inheritance:

the phenotype is determined by interactions among the alleles of several genes

Some example of a polygenic inhertiance would be _____

hair color, skin color, eye color, and height

Sex-linked inheritance involves genes on the ___

sex chromosomes

An X-linked allele determines the phenotype in ___

males since there is no corresponding allele on the Y chromosome

Some example of sex-linked inheritance are _____

red-green color blindness, hemophilia (some forms), and Duchenne muscular dystrophy

Strict dominance is when one allele ____

dominates the other allele and determines the phenotype

Some examples of a dominant allele are ____

freckles, myopia, hyperopia, Rh factor, Huntington disease, and more

Codominance is when both alleles are ____

expressed in the phenotype

Some example of a codominance are ___

type AB blood, structure of albumins, and structure of transferrins

Incomplete dominance is when two different alleles _____

produce intermediate traits in the phenotype

An example of an incomplete dominance would be ___

hemoglobin A production and hemoglobin S production

If a father is homozygous for normal pigmentation, all of the children will have the genotype Aa, and will have _____

normal skin pigmentation

If the father is heterozygous for normal skin pigmentation, the probability that a child will have normal pigmentation is _____

reduced by fifty percent

A man has only one X chromosome, so whichever allele that chromosome caries determines whether he has ____

normal color vision or is red-green color blind

News flash, you are not identifical to either of your ____

parents, or your sibling

What are the causes of variations?

crossing over during meiosis, independent assortment during meiosis, mutations from DNA replication, and random fertilization

Tetrad at synapsis:

synpasis, with the formation of a tetrad during meiosis

Crossing over:

the crossing over of portions of chromatids of two homologous chromosomes

Recombination:

The exchange of corresponding segments and groups of genes increases genetic variation among the gametes produced

Different chemical groups can be attached to the DNA-causing it to be ____

activated or inactivated = imprinting

The environment can enhance or override certain ____

phenotypes

Most diseases and traits have a genetic and environmental ____

component

A zygote is a ___

single diploid cell formed by the union of an egg and a sperm

Cleavage is mitotic divison of the ____

zygote into smaller, identical blastomeres

Morula are a spheroidal stage consisting of ____

16 or more blastomeres

Blastocysts are fluid-filled, spheroidal stage with an outer mass of ____

trophoblast cells and inner mass of embryoblast cells; becomes implanted into the endometrium; the inner cell mass forms an embryonic disc and differentiates into the three primary germ layers

Enbryonic stage is a stage in which the primary germ layers ____

differentiate into organs and organ systems; ends when all organ systems are present

Fetal stage is a stage in which organs grow and mature at a cellilar level to the point of being ____

capable of supporting life independently of the mother

Ovulation releases ____

secondary oocyte

Oocyte contains all cellular organelles, nourishment, and genetic programming to support ____

embryonic development for a week

Oocyte moves through follicular wall, ovary, into ___

the uterine tube

Sperm will travel from the vagina to the ampulla of the ____

uterine tube

Capacitation:

maturation of sperm-motility, receptors exposed, and the acrosome reaction enabled

The isthmus of the uterine tube stores and "selects" the best ___

sperm

Nuclei of the ovum and spermatozoa fuse. This is fertilization.This diploid cell is now a ___

zygote

Sperm induces oocyte activation:

- acrosomal enzymes from multiple sperm create gaps between the cells of corona radiata

- a single sperm makes contact with the oocyte membrane and membrane fusion occurs

- Membrane fusion triggers oocyte activation → which leads to the completion of meiosis

- Secondary oocyte is now an ovum

Prenatal development = ____

gestation

There are three trimesters:

the first, second, and third

During the first trimester we have _____

pre-embryonic, embryonic, and early fetal development; all major organs begin to developfer

During the second trimester we have _____

development of organs and systems

During the third trimester we have _____

rapid fetal growth

The first trimester is also know as ____

fertilization and lasts about 12 weeks

Cleave in Trimester I:

divisions right after fertilization, develops into a pre-embryo, and then a blastocyst

Implantation in Trimester I:

blastocyst attaches to the endometrium

Placentation in Trimester I:

development of the placenta (allows exchange between maternal/embryonic blood)

Embryogenesis (embryonic period) in Trimester I:

formation of a viable embryo

Only about 40% of conceptions produce embryos that survive ____

first trimester

Cleavage lasts for ~6-7 days, while the pre-embryo travels the length of the ___

uterine tube

During cleavage, 3 days after fertilization the solid ball of cells is called a ___

morula

On day 4, the morula will reach the _____

uterus

After 6-7 days a ____ is formed

blastocyst

Blastocyst is a hollow ball of ____

cells

The outer-layer of the blastocyst is called ____

a trophoblast

The trophoblast of the blastocyst provide ____

nutrients to embryo, helps erode the zona pelluicda, and later becomes the placenta and secretes hormones

The inner cell mast (embryoblast) is ___

shielded from uterine environment and later will form embryo and yolk sac

On Day 7, implantation occurs. Blastocyst surface closest to inner cell mnass and attaches to ____

uterine lining (called decidua). And trophoblast cells divide and form several layers

Cytotrophoblast is the ____

inner cell layer of trophoblast

Syncytiotrophoblast is the ____

fused trophoblast cells- erodes into the endometrium and absorb the nutrients

The amniotic cavity forms between ____

embryoblast and trophoblast

Embryoblast has ____

two layers

After implantation - week 9. Hormonal changes due to ____

human chorionic gonadotropin (hCG) (from trophoblast and chorion) and progesterone and estrogen (from corpus luteum)

Key events during embryonic period"

- differentiation of cells

- formation of germ layers

- formation of extra-embryonic membranes

- formation of placenta

Ongoing signaling (induction) causes different genes to be ____

turned on in different cells

By day 12 a third layer of inner cell mass forms = ______

gastrulation

The yolk sac is the primary source of ____

nutrients for two+ weeks and blood cell formation

Amnion is the ____

fluid cushion for the developing embryo

Allantois gives rise to ____

urinary bladder (formed as an outgrowth of the yolk sac and ends up part of the umbilical cord)

Chorion covers all the other extra embryonic membranes and ____

developing embryo/fetus; site of exchange between maternal and fetal blood; part of the placenta;

The yolk sac, amnion, allantois, and chorion all develop from the ____

fetal tissue

The placenta forms from the _____

embryonic and maternal tissue

Chorionic villi extend into endometrium- embryonic blood vessels develop ___

inside

At first, chorionic villi surround the entire conceptus, but eventually they only exist on the ____

ventral side of the embryo, where they are in contact with the decidua (endometrium). The other side of the embryo has only a thin, smooth layer of chorion, with no villi.

There are three areas of the endometrium:

the capsular decidua, the basal decidua, and the parietal decidua

Capsular decidua:

thin endometrium that surrounds developing embryo

Basal decidua:

area by placenta

Fetus and placenta connected via ___

umbilical cord

The placenta places a variety of roles such as __

nutritional support, excretory, respiratory, endocrine, and immune

The nutritional role of the placenta are ____

permitting nutrients such as glucose, amino acids, fatty acids, minerals, and vitamins to diffuse from the maternal blood to the fetal blood; stores nutrients such as carbohydrates, protein, iron, and calcium in early pregnancy and releases them to the fetus later, when daily fetal demand is greater than the mother the mother can absorb from the diet

The Excratory roles of the placenta are ____

to permit nitrogenous wastes such as ammonia, urea, uric acid, and creatinine to diffuse from the fetal blood to the maternal blood so the mother can excrete them

The Respiratory role of the placenta are ____

permitting O2 to diffuse from mother to fetus and CO2 from fetus to mother

The endocrine role of the placenta are ___

secretes estrogens, progesterone, relaxin, human chorionic gonadotropin, and human chorionic somatomammotropin; allows for other hormones synthesized by the conceptus to pass into the mother's bloo,d and maternal hormones to pass into the fetal

The immune role in the placenta are ____

transfers maternal antibodies (especially IgG) into the fetal blood to confer passive immunity on the fetus