Genetics Flashcards
Examples of Chromosomal Abnormalities
- Alteration of chromosome number:
- Polyploidy—complete sets of extra chromosomes
-
Aneuploid—chromosome number not 23—trisomy (trisomy 21 = Downs Syndrome)
- nondisjunction is common cause- occurs during meiosis when there is failure to separate chromosomes ( meiosis I) or sister-chromatids (meiosis II)
- Alteration in Chromosome Structure:
- Inversions
- Deletions
- Translocations
Single-gene disorders
- caused by mutations in individual genes
- may be present on one or both alleles
_____ follows mitosis, forming two daughter or progeny cells
Cytokinesis
Which of the following statements is true about an individual who is a carrier for the cystic fibrosis (CF) gene?
- Homozygous; suffers from CF
- Homozygous; does not suffer from CF
- Heterozygous; suffers from CF
- Heterozygous; does not suffer from CF
Heterozygous; does not suffer from CF
If an individual is a carrier, they are heterozygous for the recessive trait (in this case, CF), but they do not display the trait (because the trait is recessive)
Mendels pundentt square
dominant and recessive alleles; homozygous and heterozygous
¼ = A ½ = Aa ¼ = a
Mendel’s first law
Mendel’s first law, the principle of segregation, states that the two members of a gene pair (alleles) segregate (separate) from each other in the formation of gametes; half of the gametes carry one allele, and the other half carry the other allele
involves the division of the nuclear material of a cell
Mitosis
When in cell cycle does DNA replication happen?
S phase of cell cycle maintains the genomic information using DNA polymerase
chromosome number that is not 23
aneuploid
an example is trisomy, trisome 21 is downs syndrome, a common cause is nondisjunction
two genes together might create a new phenotype
collaborative
Contains the basic genetic information, and its expression as proteins determines the various functions of that cell
DNA structure base A, T, G, C + sugar and phosphate
Meiosis I
- Homologous chromosomes line up in the middle of the cell.
- Homologous chromosomes separate to opposite sides of the cell.
- Random shuffling of maternal and paternal chromosomes occurs.
- Crossing over or exchange between homologous segments of the sister-chromatids that make up each homologous chromosome occurs.
- Random shuffling and crossing over result in genetic recombination that ensures that genetic information in the offspring is unique.
- Result is two cells that contain 23 individual chromosomes. Each of these chromosomes has two copies or is composed of sister-chromatids.
Genetic exchange of maternal and paternal information occurs during _____ through recombination
Meiosis
many genes can affect one trait
polygenic
What is semi-conservative replication?
when replicating each DNA molecule contains one original strand and one newly synthesized strand, it ensures that any mistakes or mutations introduced during the DNA replication process can be fixed
The diploid nautre of somatic cells is maintained by _____ while the haploid number in the gametes is obtained through a process called _____
Mitosis, Meiosis
Meiosis II
The result of meiosis I is two cells that each contain individual chromosomes that have been copied (sister-chromatids). There is no duplication of genetic material in between meiosis I and II. Meiosis II will involve the further separation of each of those sister-chromatids to generate four cells each with one copy of each of the 23 homologous chromosomes. Thus, from the original diploid parent cell there are now four haploid cells that contain one copy of each chromosome. Meiosis is the process that produces the gametes—sperm and ovum—that will fuse during fertilization to form the zygote
Identifies mutations associated with disease, identifies markers of disease or predictors of disease risk or likelihodd of response to certain drug treatments
Human Genome Project
one gene might depend on another
complementary
If an unaffected mother carries one normal and one mutant allele on her X chromosome, what are the chances that she will transmit the defective gene to her sons?
- 25%
- 50%
- 75%
- 100%
50%
Because a son receives the X sex chromosome from his mother (who has one normal and one mutant allele), there is a 50% chance that the mutant allele will be inherited.
The members of each pair of autosomes are also called _____
Homologues their sequences are very similar they have different “alleles” or copies of each of the genes
Multifactorial Inheritance disorders
- Caused by a combination of variations in a number of genes that together produce or predispose an individual to a serious defect
- often in concert with environmental factors
One of the chromosomes pairs consists of _______
sex chromosomes X and Y in males X and X in females the remaining chromosomes are called autosomes
Single Locus genetic disorder, autosomal dominant traits
- Marfan syndrome (connective tissue defects)
- Achondroplasia (dwarfism)
Single Locus Genetic disorder, Mitochondrial
- Affects energy metabolism
- presents with multiple copies
- Is inherited from the mother only
Involves the reduction divisions that take the chromosomal content of germline cells from diploid (23 pairs of chromosomes) to haploid (23 individual chromosomes)
Meiosis
Explain the several phases of mitosis
PMAT
- Prophase where the nuclear membrane dissolves and two copies of each chromosome (sister chromatids) attach at the centromere.
- Metaphase where the chromosomes are highly condensed and line up on the equatorial plane of the cell.
- Anaphase where the sister chromatids separate and the chromosomes are pulled apart.
- Telophase where the nuclear membrane forms around the two sets of chromosomes.
observable properties (traits) due to interaction between genotype and environment
Phenotype
Examples of Sex Chromosome disorders
-
Turner Syndrome
- absence of all or part of the X chromosome
- lack of development of ovaries/sexual characteristics
-
Klinefelter syndrome
- one or more additional X chromosome with a normal male composition (XY)
Which type of chromosome alteration generally results in normal offspring?
Deletion
Inversion
Translocation
Ring formation
Translocation
Translocation is the only chromosomal alteration where no genetic material is actually lost (chromosome parts are exchanged), so the offspring are usually normal. Offspring are translocation carriers, so their children may or may not be normal.
There are two cell divisions that occur during meiosis
Meiosis I involves the reduction division stage that results in the formation of two haploid cells per diploid cell. Homologous chromosomes separate, but sister-chromatids (copies) remain together. Meiosis II which involves an equatorial division where sister chromatids are separated.
How is the use of complementary base pairing arranged
Anti-parallel orientation Double-helix
What is chromatin made of?
DNA and protein (histones)
Mutation that introduces a stop to protein synthesis
Nonsense Mutations
Genetic Makeup
Genotype
genetic change in one of the cells of the body and cannot be transferred to the offspring or inherited
somatic mutation
both, multiple genes and the environment could affect one trait
multifactoral
Mendels second law
the principle of independent assortment, states that genes for different traits assort independently of one another in gamete production.
Single locus genetic disorder, autosomal recessive traits
- Autosomal Recessive Traits
- cystic fibrosis
- Sickle Cell Anemia
Chromosomal disorders
- caused by an excess or deficiency of genes contained within a whole chromosome or chromosomal segment
disease process associated with translocation of chromosomes 9 and 22 of the Philadelphia chromosome
chronic myeloid leukemia (CML)
Errors in the DNA sequence are called _____ which may involve changes to a single nucleotide or larger regions of DNA
mutations
a genetic change found in the gametes, thus can be transmitted to offspring or inherited
germline mutation
_____ in the genetic code means that not all mutations cause amino acid changes
- Redundancy Mutations that do not change the amino acid are called “silent”.
- Mutations that alter the amino acid are termed “missense” and may or may not alter protein structure and thus function.
- Other mutations may introduce a stop to protein synthesis and are called “nonsense”.
- Mutations may involve the addition (insertion) or removal (deletion) of nucleotides in the DNA sequence.
How many sets of chromosomes
23 pairs (autosomes and 1 set of sex chromosomes)
Single locus genetic disorder, sex linked- X-linked recessive
- Duchene Muscular Dystrophy
- Hemophilia A
Alteration of the DNA sequence (mutation) can give rise to ____
disease
Mutations can result in an aberrent protein sequence and improper protein structure can affect _____
function
complete sets of extra chromosomes
polyploidy
___ are diploid, having two copies of each chromosome, while gametes are haploid, having only one copy of each chromosome
Somatic cells contains 23 pairs of chromosomes within the nucleus of that cell
