Chapter Four Flashcards
Inheritance of Craniofacial Anomalies
Craniofacial anomalies tend to _____in families.
Risk for recurrence is _____.
It depends on interactions of ______and ______factors.
recur
variable
environmental and genetic
Cell anatomy
Image
Deoxyribonucleic Acid (DNA)
Located in the ______of the cell
Consists of nucleotides which contain:
_______ (deoxyribose) chemically bonded to:
Nitrogenous base
_____—adenine (A) and guanine (G)
______—thymine (T) and cytosine (C)
________—links the nucleotides together at the 5th and 3rd carbons of the sugar
nucleus
A5-carbon sugar
Purines
Pyrimidines
Phosphate group
Deoxyribonucleic Acid (DNA)
DNA forms long _____(macromolecules) composed of repeating structural units.
Two strands coil together to form a ______.
______is always paired with a specific pyrimidine in the opposite strand (e.g., A-T and C-G pairs).
polymers
double helix
Purine
Replication
Replication is the process of making ….
One strand of the double helix allows DNA to serve as a template for its own ______.
two identical DNA molecules from one.
replication
Process of replication:
Double helix is unwound.
Complementary strands are separated.
Nucleotides are added to each single strand sequentially, forming new complementary strands.
The result is two identical double helix molecules of DNA.
Genes and Chromosomes
Gene:
Chromosome:
Gene—submicroscopic functional unit of heredity, consisting of a discrete segment of a DNA strand within a chromosome
Chromosome—a single, linear double strand of DNA with associated proteins
Genes
______are found in each chromosome.
Genes consist of the following:
A _____region—starting point for the gene’s activity and serves as an on/off switch
A _____region—contains information needed to make a functional protein
_______elements—determine how much of the protein will be made
Thousands
promoter
coding
Regulatory
Changes in the coding region of a gene may lead to _____(deletions or insertions) that ____gene function.
Mutations can result in various ______or _______.
mutations; disrupt
diseases or malformations
_______—variability in genes among individuals
Polymorphism is _____in virtually all genes.
It contributes to the _____of each individual.
New variants that improve _____may become more common over time.
New variants that lead to disease will remain rare or be ______.
Polymorphism
common
uniqueness
function
eliminated
Ribonucleic Acid (RNA)
Similar to DNA, but
Are located in the _____, not the nucleus
Is a ____strand rather than a double strand
Has _____as the sugar rather than dextrose
Has the _____(U) in place of thymine (T)
cytoplasm
single
ribose
pyrimidine uracil
Transcription—
a process in which a complementary strand of DNA is created with a single-strand template
Ribonucleic Acid (RNA)
Amino acids:
Polypeptide:
Protein:
the building blocks of proteins
a sequence of amino acids
consists of polypeptides
____determines which amino acids will be incorporated into the protein.
_______—determines the amino acid sequence for a polypeptide
______—segments of the coding region that are spliced together to form a continuous RNA coding sequence
_____—segments between exons that are spliced out follow
RNA
Coding region
Exons
Introns
Messenger RNA or mRNA
RNA that has had the introns _____
Is transported from the nucleus to the cytoplasm to function as a template for ______
_______—organelles that attach to mRNA and translate nucleotides into the specified polypeptide (amino acid sequence), forming a template for protein synthesis
removed
protein synthesis
Ribosomes
Chromosomes
Linear double strands of DNA with associated ______
Function to _____and compact the DNA in a cell
proteins
organize
The main function of DNA is***
…
The main function of a gene;
passing on traits to offspring
_____—a complete set of instructions for a particular organism or species
_____—a visual profile of an individual’s chromosomes
Genome
Karotype
_______—narrowed region of each chromosome that is important for cell division
Types of chromosomes:
______—contain a centrally located centromere
______—centromere is off center, leading to a short “p” arm and a long “q” arm
_______—centromere is close to one end of the chromosome
Centromere
Metacentric chromosomes
Submetacentric chromosomes
Acrocentric chromosomes
Each chromosome contains:
A ______—narrowed region that is important for cell division
A chromosome may contain:
A ____—short arm on each side
A ____—long arm on each side
centromere
“p” arm
“q” arm
Each pair of chromosomes is numbered from 1 to __.
Chromosomes from 1 to 22, called _____, are numbered according to length (longest is 1 and shortest is 22).
The ____pair, called the sex chromosomes (X and Y), determine gender.
Females have two __chromosomes (one from each parent), written as 46, XX.
Males have an __(from the mother) and a __(from the father), written as 46, XY.
23
autosomes
23rd
X
X and Y
Chromosomes can be ____to reveal light and dark colored bands.
____—a schematic drawing of the banding pattern of a chromosome
stained
Ideogram
Specific genes are labeled by the chromosome number, arm (“p” or “q”) and band number to indicate its _____relative to the centromere and the other bands on that arm.
Chromosomes are used to describe the rough location of ____in gene mapping studies.
Example: lp36 means the gene is on the short arm of chromosome 1 in the band labeled 36
location
genes
Cell Cycle
Cells alternate between states of active ____and _____.
______—the process of preparing for and undergoing cell division
Frequency depends on the ______and the ______of the organism at the time.
Steps are similar for all types of somatic cells (all cells except, those for _____).
division and nondivision
Cell cycle
type of cell and rate of growth
reproduction
Two major processes:
_____—process of separating duplicated chromosomes and reconstitution of two cell nuclei
Takes place in the ______cells
An identical set of chromosomes is distributed to each _____cell
Results in daughter cells that have the same number of chromosomes (46) as the _______
_______—the separation of the cell cytoplasm to form two distinct cells with separate cell membranes
Mitosis
somatic
daughter
parent cell
Cytokinesis
Meiosis:
Meiosis occurs only in the production of _____, which are sperm from the testes and ova (eggs) from the ovaries.
Process results in ___chromosomes rather than 46.
When sperm and ova combine to form a ____, the organisim will have 46 chromosomes.
Cells division results in cells that each have a single ____of each chromosome.
______—the time between cell division
gametes
23
zygote
copy
Interphase
Chromosomal Abnormalities
Nondisjunction—
Monosomy:
.
Monosomy X results in ______
failure of chromosome to separate during cell division
Loss of one copy of a chromosome results in only a single copy of a chromosome
Turner syndrome.
Trisomy:
Trisomy is caused by gaining one extra copy of a chromosome, for a total of _____chromosomes
Trisomy can occur for 13, 18, 21 (Down syndrome), or X.
three
______—when the cells have different genetic contents in a single individual
______—when part of a chromosome becomes separated and lost
Mosaicism
Deletions
______—when a part of a chromosome is duplicated
_______—when there is a transfer of genetic material between two or more chromosomes
______—when a portion of a chromosome is turned 180° from its usual orientation
Note: Small mutations involving single genes are more common than chromosomal abnormalities.
Duplications
Translocations
Inversions
Normal and deleted human chromosome 4 with ideograms
Associated with ________
Wolf-Hirschhorn syndrome
Chromosomes are _____during certain stages of the cell cycle, to be easily viewed under a microscope.
For abnormalities that are too small to be seen with routine analysis, a special technique called fluorescence in situ hybridization (____) is used in a cytogenetics lab.
FISH is needed to identify deletions on chromosome 22qll.2, associated with _______
condensed
FISH
velocardiofacial syndrome
______ (cell genetics)—a branch of genetics dealing with the structure and function of the cell, particularly the chromosomes
_____—caused by deletions that contain several genes
Cytogenetics
Contiguous gene syndromes
______—patterns of inheritance first described by Mendel in his studies on peas in 1866
Patterns include:
1.
2.
3.
Allele—
Mendelian inheritance
- Autosomal recessive
- Autosomal dominant
- X-linked patterns
a copy of a gene
Pattern of inheritance of a trait depends on whether the individual is:
_______—has the same allele of the gene for a trait
_____—has two different alleles of the gene for a trait
Homozygous
Heterozygous
Pedigree—
a pictorial representation of family members and their line of descent
Autosomal Recessive Inheritance
_____—heterozygous individuals who have one normal and one abnormal copy of a gene but are without detectable abnormalities as a result
_____—a group of features or typical characteristics of a genetic condition
Carriers
Phenotype
Autosomal Recessive Inheritance
_______—a trait that manifests only when mutations are present in both copies of a gene
Only ______individuals will have features typical of the phenotype of an autosomal recessive condition.
Autosomal recessive
homozygous
When two heterozygous carriers of an autosomal recessive condition mate:
There is a 25% risk that the child will receive a copy of the abnormal gene from each parent and become affected.
There is a 50% risk that the child will receive a single copy of the abnormal gene from one parent and become a carrier.
_______—mating between related individuals
Leads to increased risk that the both members of the couple carry the same disease-causing mutations of the same genes
________—a condition where a specific phenotype can be caused by mutations of different genes
Consanguinity
Heterogeneity
Autosomal Dominant Inheritance
_________—a trait that manifests when mutations are present in only one copy of a gene
Both ______ and _______individuals will have features typical of the phenotype of an autosomal dominant condition.
Autosomal dominant
homozygous and heterozygous
When two individuals with a dominant condition mate:
There is a ____% chance that they will pass the condition to their offspring, who will be homozygotes with two copies of the defective gene.
100
When one individual with a dominant condition and an unaffected partner mate:
There is a ____% risk with each pregnancy of passing the condition to their offspring (who will be heterozygotes).
50
When two individuals with the same autosomal dominant disorder mate:
There may be unaffected children if both parents are heterozygotes, with one normal and one abnormal allele.
_________—the lack of a recognizable phenotype in an individual who carries a gene for an autosomal dominant trait or condition
_________—where a single mutant gene can affect multiple, unrelated systems (e.g., heart, skin, bones, etc.)
Incomplete penetrance
Pleiotropy
X-linked inheritance—caused by genes on the X chromosome
Affects mostly _____because they inherit only one allele of the X chromosome, whereas females inherit two copies
males
X-linked recessive conditions:
These affect ____almost exclusively
Females have only a ____effect or no effect.
Carrier females transmit the defective genes to ___% of their sons, who will be affected.
Carrier females transmit the defective genes to 50% of their daughters, who will be carriers.
Affected males pass the gene to ____% of their daughters
There is no father-to-son transmission because fathers do not give an __chromosome to their sons.
males
mild
50
100
X
X-linked dominant conditions: rare, with only a few known disorders
Affected males:
Transmit the disorder to all _____
Do not transmit to ____, because they receive the Y chromosome from the father
Many X-linked dominant disorders that are ____to males
Affected females:
Are more often affected than males
Can transmit the disorder to offspring of both _____
daughters
sons
lethal
sexes
Non-Mendelian Inheritance
Inheritance that does not follow the basic rules of Mendelian inheritance includes:
1.
2.
3.
- Multifactorial inheritance
- Anticipation
- Imprinting
_______—when disorders result from an interaction of multiple genes with environmental influences
_______—environmental factors known to increase risks for birth defects
Multifactorial inheritance
Teratogens
Multifactorial Inheritance
Two categories of multifactoral inheritance abnormalities:
1.
2.
- Continuous variation abnormalities
2. Threshold abnormalities
Continuous variation abnormalities
These include traits on a continuum, such as height, weight, intelligence, and blood pressure.
Border between normal and abnormal is subjective and a matter of arbitrary definition.
Threshold abnormalities
These include cleft lip/palate, pyloric stenosis, and neural tube defects.
Trait is either present or absent.
As the number of risk factors increases, the additive risk may cross a threshold, resulting in expression of the trait.
Multifactorial Inheritance
Recurrence risk
Increased with greater _____
Increased in close relatives because:
They share _______.
They have similar _____risk factors.
severity
genetic backgrounds
environmental
___________—a tendency in certain inherited disorders to have more severe manifestations or an earlier age of onset with succeeding generations
Anticipation
______—the tendency for some genes to function differently, depending on whether they were inherited maternally or paternally
If the gene is maternally imprinted, the allele inherited from the mother is not _____.
If the gene is paternally imprinted, the allele inherited from the father is not _____.
Imprinting
expressed
expressed
