Mccurdy Human genetics test 1

Preimplantation genetic diagnosis

Preimplantation genetic diagnosis

analyzes an embryo before it implants. Only possible in IVF

primary spermatocyte

a cell that divides to form two secondary spermatocytes

what makes primary spermatocytes?

Spermatogonium

secondary spermatocytes

Haploid cells resulting from the first meiotic division of spermatogenesis. Secondary spermatocytes are ready to enter meiosis II. 1 chromosome set

mitosis phases

prophase, metaphase, anaphase, telophase

oogonia

an immature female reproductive cell that gives rise to primary oocytes by mitosis

primary oocyte

a cell that divides to form the polar body and the secondary oocyte

secondary oocyte

An oocyte in which the first meiotic division is completed. The second meiotic division usually stops short of completion unless fertilization occurs.

what happens to polar bodies

apoptosis or absorbed by the body

is the second polar body made all the time?

No, because meiosis 2 is halted until fertilization. No fertilization, no 2nd polar body.

what cell is more likely to have an abnormal amount of chromosomes?

Eggs, and probability goes up with age. the longer the cell is frozen in prophase one, the more likely it is for problems to arise.

why do sperm have more mutations?

they divide more frequently since their replication occurs every 16 days.

Mendel's Method

use the pollen from a male plant on a female plant and let them reproduce based on traits

true breeding

term used to describe organisms that produce offspring identical to themselves if allowed to self-pollinate

P generation

Parental generation, the first two individuals that mate in a genetic cross

F1 generation

the first generation of offspring obtained from an experimental cross of two organisms

F2 generation

Offspring resulting from interbreeding of the hybrid F1 generation.

Mendel's Law of Segregation

the two copies of a gene segregate from each other during transmission from parent to offspring

Dominant

Describes a trait that covers over, or dominates, another form of that trait.

recessive

trait of an organism that can be masked by the dominant form of a trait

phenotype ratio of a monohybrid cross

3:1 if complete dominance and both parents are heterozygous

testcross

cross between an organism with an unknown genotype and an organism with a recessive phenotype

dihybrid cross

Cross or mating between organisms involving two pairs of contrasting traits

number of gamete combinations

2^n where n is the number of heterozygous genes

Probability

likelihood that a particular event will occur

Product Rule

the probability that two or more independent events will occur is equal to the product of their individual probabilities

Sum rule

probability of the occurrence of at least one of two mutually exclusive events is the sum of their individual probabilities

forked-line method

Diagram using product law of probabilities to predict genotypic and phenotypic frequencies

do many human traits show simple single gene inheritance?

no, most human traits are determined by several gene interactions.

what human genes follow simple gene inheritance?

ABO blood types, red-green color vision, and many genetic diseases like cystic fibrosis or Huntingtons.

Hemophilia C

Factor XI deficiency. C is not X-linked like A and B, it is also milder

de novo mutation

an alteration in a gene that is present for the first time in one family member as a result of a mutation in a germ cell (egg or sperm) of one of the parents or in the fertilized egg itself

in a pedigree if an individual is unaffected, do we include the homozygous recessive allele in probability calculations?

No, because the probability of him being homozygous recessive is 0 if the individual is unaffected.

Duchenne muscular dystrophy

A human genetic disease caused by a sex-linked recessive allele; characterized by progressive weakening and a loss of muscle tissue.

X-linked dominant

a mode of genetic inheritance by which a dominant gene is carried on the X chromosome. more common in females than males.

Y-linked inheritance

Only males have Y chromosomes, passed from fathers to sons, all Y-linked traits are expressed. very rare.

Y linked hearing impairment

transmitted from fathers to sons in one particular family

Y chromosome infertility

usually caused by deletions of genetic material in regions of the Y chromosome called azoospermia factor (AZF) A, B, or C. Genes in these regions are believed to provide instructions for making proteins involved in sperm cell development.

haplosufficient

describes a gene that, in a diploid cell, can promote wild-type function in only one copy (dose)

Haploinsufficiency

The appearance of a mutant phenotype in an individual cell or organism that is heterozygous for a normally recessive trait. one copy creates a normal product, but the other creates a protein that interferes with the other.

Fibrillin-1 function

joint stuff.

dominant negative mutation

Exerts a dominant effect. A heterozygote produces a nonfunctional altered protein that also prevents the normal gene product from functioning

gain of function mutation

causes the appearance of a new trait or function or causes the appearance of a trait in inappropriate tissue or at an inappropriate time

incomplete penetrance

Not all individuals with a mutant genotype show the mutant phenotype. easiest to spot in a dominant pedigree

penetrance

The percentage of individuals with a particular genotype that actually displays the phenotype associated with the genotype.

s phase

Each chromosome still has 46 chromosomes, but 92 chromatids.

varying expressivity

gene shows its effect to different degrees in different members of a population

pleiotropy

A single gene having multiple effects on an individuals phenotype

variable penetrance

not all individuals of the same genotype show the expected phenotype

variable penetrance and variable expressivity

Some people have the trait, some do not, and those that do show very different variations on the trait.

modifier genes

genes that enhance or dilute the effects of other genes.

sometimes different copies of genes

Can be expressed to different levels. Sometimes, a normal gene will be expressed more than the diseased one.

Environmental factors

Can affect phenotype.

incomplete dominance

A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits.

heterozygous advantage

Heterozygous alleles have greater selective advantage than either homozygous condition.

over dominance

A condition in which the heterozygote genotype expresses a phenotype outside the range of the homozygous phenotype. Think sickle cell giving an advantage over malaria.

Cystic fibrosis heterozygous

May have aided in protection from typhoid

Codominance

A condition in which neither of two alleles of a gene is dominant or recessive.

lethal phenotype

A phenotype (usually homozygous) that is lethal or results in premature death. Not counted in phenotypic ratios.

epistasis

A type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited.

Recessive epistasis

when the recessive allele of one gene masks the effects of either allele of the second gene. 9:4:3

duplicate dominant epistasis

homozygous recessive genotypes for both genes are required for an observed result. 15:1

duplicate recessive epistasis

two recessive alleles at either of two loci are capable of suppressing a phenotype 9:7

dominant epistasis

when the dominant allele of one gene masks the effects of either allele of the second gene 12:3:1

Carrier DNA screening

available for disorders that have a relatively high prevalence in the population or in a particular ethnic group Analyzes DNA for the presence of the most common disease-causing mutations

Cell-free fetal DNA testing

Uses the mothers blood to screen- performed at >10wks until delivery

• T21: 99% sensitivity, specificity** the best test

• T18: 92% sensitive

• T13: 80% sensitive

amniocentesis

A technique of prenatal diagnosis in which amniotic fluid, obtained by aspiration from a needle inserted into the uterus, is analyzed to detect certain genetic and congenital defects in the fetus.

chorionic villus sampling

sampling of placental tissue for microscopic and chemical examination to detect fetal abnormalities.

Newborn screening

The analysis of a neonate's blood for metabolic or genetic disorders to prevent mental retardation, disability or death

Karyotyping

Looking at the chromosomes from a blood test.