Genetics Flashcards
What are the building blocks of DNA?
A, T, C, G
A = Adenine, T = Thymine, C = Cytosine, G = Guanine
What structure holds the building blocks of DNA together?
Double Helix
The double helix structure is supported by phosphate and deoxyribose sugar.
What is a nucleotide in the context of DNA?
1 strand of DNA
A nucleotide consists of a phosphate group, a deoxyribose sugar, and a nitrogenous base (A, T, C, or G).
How many pairs of chromosomes do humans have?
23 pairs
This totals 46 chromosomes.
What are chromatids?
Replicated chromosomes connected by a centromere
They become visible during cell division.
What is a karyotype?
The organization of condensed chromosomes from largest to shortest
It includes banding patterns for identification.
Define homologous chromosomes.
Chromosome pairs with the same gene sequence inherited from parents
They may have different alleles.
What are autosomes chromosomes?
Chromosomes that contain genes in functioning organisms, regardless of sex
Humans have 22 pairs of autosomes.
What are sex chromosomes?
Chromosomes that determine biological gender
Females have XX and males have XY.
What is spermatogenesis?
The production of sperm through meiosis
Starts with spermatogonium (2n).
What is oogenesis?
The production of eggs through meiosis
Starts with oogonium (2n).
What are diploid cells?
Cells containing the full set of 23 pairs of homologous chromosomes
Also referred to as ‘2n’.
What are haploid cells?
Cells containing only 1 set of chromosomes (23)
They are only found in meiosis and are referred to as ‘n’.
What is the main function of mitosis?
To duplicate the stem cell into a replica
Resulting in a diploid cell (2n).
During which phase does crossing over occur in meiosis?
Prophase I
This involves synapsis and the formation of tetrads.
What happens during anaphase I of meiosis?
Spindle fibers pull homologous chromosomes to opposite poles
haploid cells are created
Each chromosome consists of 2 sister chromatids.
What are chromosome abnormalities?
Changes in chromosomes that occur during S-phase of interphase
They include deletion, duplication, inversion, substitution, and translocation.
What is aneuploidy?
The production of daughter cells with more or less chromosomes
It results from nondisjunction.
Define genotype.
The combination of alleles (e.g., YY, Yy, yy)
It represents the genetic makeup of an individual.
Define phenotype.
The expressed genetic trait (e.g., Yellow, Blond)
It is the observable characteristic of an organism.
What is a dominant allele?
The gene that takes priority over another for the phenotype
It masks the effect of a recessive allele.
What is a Punnett square used for?
To show the probability of offspring genotype and phenotype
It helps visualize genetic crosses.
What does the law of segregation state?
Alleles of a gene randomly separate into individual gametes
Each gamete only gets 1 copy of the allele from the Mom and Dad.
What are linked genes?
Genes located closely on the same chromosome that do not segregate during meiosis
They tend to be inherited together.
What are carriers in genetics?
Individuals who carry recessive alleles but express a dominant phenotype
Example: A heterozygous woman with normal vision but carries colorblindness.
What are X-linked traits?
Traits found only on the X chromosome
Males express these traits because they have only one X chromosome.
Define incomplete dominance.
A condition where the phenotype is a blend of both alleles
Example: Red and white flowers producing pink offspring.
What is co-dominance?
When both dominant alleles are expressed in a heterozygous individual
Example: AB blood type shows both A and B antigens.
What are multiple alleles?
More than two alleles for a gene
Example: Blood types (I(A), I(B), i).
