Heredity Flashcards
Distinct segments of chromosomal DNA that are transmitted from parent to offspring and cary the genetic code
Genes
Genes determine the
Hereditary traits
Each gene may have multiple variants or
Alleles
Chromosomes and their genes exist in
Pairs
How many chromosomes in humans
46 chromosomes (23 pairs)
Chromosomes that are not involved in sex determination are
Autosomes (22 pairs of these or 44 chromosomes)
The paired autosomes carry genes for the
Same traits at the same sites as each other
Each variant of autosomes is known as an
Allele
Homozygous means
Botha genes are same
Heterozygous means
The two genes differ
Dominant genes are always
Expressed, if present
Dominant genes need to inherit from only
One parent
Recessive genes are only expressed if
Homozygous
(Need to inherit from both parents)
Recessive traits MUST HAVE
Homozygous alleles
Phenotype refers to
An observable or testable characteristic
(Ex. Eye colour, blood type)
Genotype refers to
Ones genetic makeup
Homozygous recessive example
bb
*phenotype is recessive
Homozygous dominant example
BB
*phenotype is dominant
Heterozygous example
Bb
A punnet square is used to determine
The probability of inheriting genetic traits
Capital letters represent
Dominant allele
Lower case letter represents
Recessive allele
Reproductive cells are produced by
Meiosis
Meiosis is the process that divides the # of chromosomes in half. How many meiotic divisions
2
The first meiotic division distributes the chromosome pair into
Separate cells
The second meiotic division separates the strands of the duplicated chromosome and
Distributes to an individual gamete
Sex chromosomes determine the
Sex of the offspring
Are sex chromosomes matched?
No
Female chromosome is larger and is depicted as?
X
Male chromosome is small and mainly determines sex. Depicted by
Y
Non sexual traits carried on the sex chromosome are sec linked traits and most are
X-linked traits
By meiosis each sperm received
An X or a Y
By meiosis each egg receives only
An X
Normal females have
2 X chromosomes
- XX as pair 23
Normal males have
X and Y chromosome
-XY as pair 23
Traits carried on a sex chromosome are termed
Sex linked traits
Most sex linked traits are carried on the
X chromosome and are best described as X-linked
Most sex linked traits are
Recessive
Hereditary traits can be
Observable (skin, eyes, hair color, facial features)
Or less clearly defined (weight, body build, life span, disease susceptibility)
Human traits and genetic diseases can be determined by
A single pair of genes (less common)
Or multifactorial inheritance
Multifactorial inheritance refers to
Result of 2 or more gene pairs acting together
-can include environmental factors
-produces a wide range of variation in traits such as weight, height, skin colouration
Gene expression is influenced by
Gender
Other genes (codominance, incomplete dominance)
The environment
Genetic mutation is a change in the
Genetic code within a gene or chromosome
Genetic mutation may be
Hereditary
Genetic mutation is often caused by
Mutagens
What are some agents that cause mutations
Chemicals, radiation, drugs or viruses
Genetic mutation: what agents cause damage during embryonic development
Teratogenic agents (teratogens)
Chromosomal breakage is aka
Non disjunction
Most common non hereditary genetic disorder
Down syndrome or trisomy 21
*3 chromosomes at the 21 position so 47 in total
What is turner syndrome
Aka monosomy X
Only one sex cell is present, the X chromosome
-commonly self aborts (1%survive and are born)
Chromosomal disorder where 1 in 600 males are affected. Caused by the presence of 2 or more X chromosomes in a male. Affects males physical and cognitive development
Kkinefelter Syndrome
Congenital disease means
Present at birth
(May or may not be hereditary)
Hereditary diseases means
Genetically transmitted
(May not be evident at birth and manifests later in life)
Huntington disease is hereditary and is characterized by? What chromosome does it affect?
Characterized by progressive degeneration of the brain
Affects chromosome 4.
Causes of congenital disorders?
Often idiopathic (unknown cause)
Infections/toxins transmitted from mother
Teratogen
Ionizing radiation
Alcohol intake
Cigarette smoking
Poor nutrition
Karyotype refers to
The number and visual appearance of chromosomes of a cell.
-an individuals complete set of chromosomes
What is amniocentesis
Involves collection of fetal cells floating in amniotic fluid used to detect abnormalities
