Chapter 5: Genetic Control Of Cell Function and Inheritance Flashcards
Define mitosis
mitosis: A type of indirect cell division that occurs in somatic cells and results in the formation of two daughter nuclei containing the identical complements of the number of chromosomes characteristic of the somatic cells of the species.
Define meiosis
meiosis: The division of a sex cell as it matures, so that each daughter nucleus receives one half of the number of chromosomes characteristic of the somatic cells of the species.
Define karyotype
karyotype: The total chromosomal characteristics of a cell; or the micrograph of chromosomes arranged in pairs in descending order of size.
What is a gene?
A gene is a locatable segment or segments of DNA sequence that encodes a set of functional products, typically proteins
p
proteome is a relatively new term, created to define the complete set of proteins encoded by a genome.
n
nucleotides, which consist of phosphoric acid, a five-carbon sugar called deoxyribose, and one of four nitrogenous bases. These nitrogenous bases carry the genetic information and are divided into two groups: the pyrimidine bases, thymine (T) and cytosine (C), which have one nitrogen ring; and the purine bases, adenine (A) and guanine (G), which have two.
c
chromosomes, discrete bundles made up of one continuous, linear DNA helix
n
chromosomes, discrete bundles made up of one continuous, linear DNA helix
cA sequence of three of these bases forms the fundamental triplet code for one of the 20 amino acids used in protein synthesis in humans. This triplet code is called a codon.
h
l
Several repair mechanisms exist, and each depends on specific enzymes called endonucleases that recognize distortions of the DNA helix, cleave the abnormal chain, and remove the distorted region. The gap is then filled when the correct nucleotides, identified by a DNA polymerase using the intact complementary strand as a template, are added to the cleaved DNA. The newly synthesized end of the segment is then joined to the remainder of the DNA strand by a DNA ligaser
h
It is the small DNA sequence variation (one in every 1000 base pairs) that is thought to account for the individual differences in physical traits, behaviors, and disease susceptibility. These variations are sometimes referred to as single nucleotide polymorphisms (from the existence of more than one morphologic form in a population), or SNPs
i
a genome-wide map of these variations as haplotypes (a combination of SNPs at adjacent locations which are inherited together) with the intent of providing a link between genetic variations and common complex diseases such as cancer, heart disease, diabetes, and some forms of mental disease (the International HapMap Project is discussed in the section under gene technology).
mtDNA
mitochondrial DNA
g
Genetic disorders of mtDNA, although rare, commonly affect tissues such as those of the neuromuscular system that have a high requirement for oxidative metabolism
Which ribonucleic acid (RNA) structure translates the instructions and provides the machinery for protein synthesis? Transfer RNA Messenger RNA Instructor RNA Ribosomal RNA
Ribosomal RNA
r
RNAdiffers from DNA in three aspects of its structure. First, RNA is a single-stranded rather than a double-stranded molecule. Second, the sugar in each nucleotide of RNA is ribose instead of deoxyribose. Third, the pyrimidine base thymine in DNA is replaced by uracil in RNA.
g
Genes are transcribed by enzymes called RNA polymerases
Where does the complex made of polymerases bind to the DNA?
This complex binds to the double-stranded DNA at a specific site called the promoter region. Within the promoter region is the so-called “TATA box” that contains the crucial thymine-adenine-thymine-adenine sequence that RNA polymerase recognizes and binds to, starting the replication process (
e
This complex binds to the double-stranded DNA at a specific site called the promoter region. Within the promoter region is the so-called “TATA box” that contains the crucial thymine-adenine-thymine-adenine sequence that RNA polymerase recognizes and binds to, starting the replication process (
What are the majority of the proteins made from DNA?
This complex binds to the double-stranded DNA at a specific site called the promoter region. Within the promoter region is the so-called “TATA box” that contains the crucial thymine-adenine-thymine-adenine sequence that RNA polymerase recognizes and binds to, starting the replication process (
w
There are three types of RNA: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA)
What is a peptide? What is a polypeptide?
A compound consisting of two or more amino acids linked in a chain. A polypepetide is a chain of 100 to 3000 amino acids.
Hoe does mRNA get out of the nucleus and into the cytoplasm?
it diffuses through the nuclear pores.
What is the mysterious complex going into my TATA box?
RNA polymerase along with transcription factors
c
The folding of many proteins is made more efficient by special classes of proteins called molecular chaperones.
d
Disruption of chaperoning mechanisms causes intracellular molecules to become denatured and insoluble. These denatured proteins tend to stick to one another, precipitate, and form inclusion bodies. The development of inclusion bodies is a common pathologic process in Parkinson, Alzheimer, and Huntington diseases.
g
The degree to which a gene or particular group of genes is active is called gene expression
t
transcription factors can function to increase or decrease transcriptional activity of the genes.
b
Genes transmit information contained in the DNA molecule as a triplet code consisting of an arrangement of the nitrogenous bases of the four nucleotides (i.e., adenine, guanine, thymine [or uracil in RNA], and cytosine).
m
The maternal and paternal chromosomes of a pair are called homologous chromosomes (homologs)
What are autosomes, and how many pairs do I have?
They are the 22 non-sexual chromosomes.
c
This inactive chromatin mass is called a Barr body. The genetic sex of a child can be determined by microscopic study of cell or tissue samples for the presence of a Barr body. For example, the cells of a normal female have one Barr body and therefore a total of two X chromosomes. A normal male has no Barr bodies.
m
During meiosis I, homologous chromosomes pair up, forming a double-structured chromosome containing four chromatids (four strands) and therefore called a tetrad (two chromatids per chromosome). They are also sometimes called bivalents.
c
While in meiosis I, an interchange of chromatid segments can occur (Fig. 5-8). This process, called crossing over, allows for new combinations of genes, increasing genetic variability.
d
During cell division II, the 23 double-stranded chromosomes (two chromatids) of each of the two daughter cells from meiosis I divide at their centromeres (central regions where the chromatids meet).
c
Cytogenetics is the study of the structure and numeric characteristics of the cell’s chromosomes.
c
a drug called colchicine is used to arrest mitosis before the chromosomes separate.
c
If the centromere is in the center and the arms are of approximately the same length, the chromosome is said to be metacentric; if it is not centered and the arms are of clearly different lengths, it is submetacentric; and if it is near one end, it is acrocentric.
p
The short arm of the chromosome is designated as “p” for “petite,” and the long arm is designated as “q” for no other reason than it is the next letter of the alphabet.
v
The arms of the chromosome are indicated by the chromosome number followed by the p or q designation (e.g., 15p).
x
Chromosomes 13, 14, 15, 21, and 22 have small masses of chromatin called satellites attached to their short arms by narrow stalks.
chiasma definition
a point at which paired chromosomes remain in contact during the first metaphase of meiosis, and at which crossing over and exchange of genetic material occur between the strands.
c
Xp22 refers to band 2, region 2 of the short arm (p) of the X chromosome.
Define allele
half of a gene pair (from one parent)
Define Autosomal Dominance and list diseases
One mutant allele in the pair: achondroplasia, adult polycystic kidney disease, huntington chorea, marfan syndrome
Define Autosomal recessiveness and list diseases
Both parents carry and all children will have or carry: cystic fibrosis, glycogen storage disease, oculocutaneous albinism, phenylketonuria
List recessive sex linked diseases
Duchenne muscular dystrophy, hemophilia, fragile X, Bruton Hypergammaglobulinemia, color blindness, breast cancer
e
Expressivity refers to the manner in which the gene is expressed in the phenotype, which can range from mild to severe. Penetrance represents the ability of a gene to express its function. Seventy-five percent penetrance means 75% of persons of a particular genotype present with a recognizable phenotype. Syndactyly (webbed fingers or toes) and blue sclera are genetic mutations that often do not exhibit 100% penetrance.
m
Multifactorial inheritance is similar to polygenic inheritance in that multiple genes at different loci affect the outcome; however, environmental effects on the genes also affect the outcome.
v
Many other gene–gene interactions are known. These include epistasis, in which a gene in one locus masks the phenotypic effects of a gene at a different locus; multiple alleles, in which more than one allele affects the same trait (e.g., ABO blood types); complementary genes, in which each gene is mutually dependent on the other; and collaborative genes, in which two different genes influencing the same trait interact to produce a phenotype neither gene alone could produce.
x
For some human genes one of the alleles is transcriptional inactive (no RNA produced), depending on the parent from whom the allele is inherited. For example, an allele from the mother would be active and that from the father would be inactive. This process of gene silencing was given the name genomic imprinting by Helen Crouse in 1960. It is now more commonly known as genetic imprinting.
x
ovarian teratomas (tumors made up of various cell types derived from an undifferentiated germ cell) and hydatidiform moles (gestational tumors)
c
uniparental disomy. This occurs when two chromosomes of the same number are inherited from one parent. Normally, this is not a problem except in cases where a chromosome has been imprinted by a parent. If an allele is inactivated by imprinting, the offspring will have only one working copy of the chromosome, resulting in possible problems.
d
A haplotype is a set of DNA variations, or polymorphisms, that tend to be inherited together. A haplotype can refer to a combination of alleles or to a set of single nucleotide polymorphisms (SNPs) found on the same chromosome.
j
he haplotype map, focuses on identifying the slight variations in the human genome that influence an individual’s susceptibility to disease and responses to environmental factors such as microbes, toxins, and drugs.
c
Many methods have been used for developing genetic maps. The most important ones are family linkage studies, gene dosage methods, and hybridization studies
c
Males, because they have one X and one Y chromosome, are said to be hemizygous for sex-linked traits. Females can be homozygous (normal or mutant) or heterozygous for sex-linked traits. Heterozygous females are known as carriers for X-linked defects.
d
One autosomal recessive disorder that has been successfully diagnosed prenatally by linkage studies using amniocentesis is congenital adrenal hyperplasia (due to 21-hydroxylase deficiency), which is linked to an immune response gene
c
Postnatal linkage studies have been used in diagnosing hemochromatosis
d
Dosage studies involve measuring enzyme activity.
d
In situ hybridization involves the use of specific sequences of DNA or RNA to locate genes that do not express themselves in cell culture. Deoxyribonucleic acid and RNA can be chemically tagged with radioactive or fluorescent markers.
s
Sites in the DNA sequence where individuals differ at a single DNA base are called single-nucleotide polymorphisms (SNPs, pronounced “snips”).
n
Pharmacogenetics addresses the variability of drug response due to inherited characteristics in individuals. With the availability of SNPs, it may soon be possible to identify persons who can be expected to respond favorably to a drug and those who can be expected to experience adverse reactions.
v
The DNA molecule is cut apart using a bacterial enzyme, called a restriction enzyme, that binds to DNA wherever a particular short sequence of base pairs is found and cleaves the molecule at a specific nucleotide site. In this way, a long DNA molecule can be broken down into smaller, discrete fragments
v
plasmid, which is a cloning vector such as a bacterial virus or a small DNA circle that is found in most bacteria,
x
a bacterial vector and the DNA fragment are mixed and joined by a special enzyme called a DNA ligase.
replication can make insulin, human growth hormone, and what else?
erythropoietin, which is used to stimulate red blood cell production; factor VIII, which is used to treat hemophilia; and tissue plasminogen activator (tPA), which is frequently administered after a heart attack to dissolve the thrombi that are obstructing coronary blood flow.
pcr
erythropoietin, which is used to stimulate red blood cell production; factor VIII, which is used to treat hemophilia; and tissue plasminogen activator (tPA), which is frequently administered after a heart attack to dissolve the thrombi that are obstructing coronary blood flow.
delivery vehicle for gene therapy. what can gene theray treat?
adenoviruses, Sterically stable liposomes. IT CAN TREAT some CANCER, some infectious diseases, and cystic fibrosis
w
To date, gene therapy has been used successfully to treat children with severe combined immunodeficiency disease (see Chapter 16) and in a suicide gene transfer to facilitate treatment of graft-versus-host disease after donor lymphocyte infusion.
sx
RNA interference (RNAi) to stop genes from making unwanted disease proteins. RNA interference is a naturally occurring process in which small pieces of double-stranded RNA (small interfering RNA [siRNA]) suppress gene expression
