A family tree that describes the interrelationships of parents and children across generations
Pedigrees are used by professionals to analyze the pattern of inheritance of a particular trait throughout a family for medical purposes
Pedigrees can be used to make predictions about future offspring
Autosomal Traits
46 autosome; 2 sex chromosomes
Standardized symbols used in pedigrees
CIRCLE: female
CROSSED OUT: deceased
SQUARE: male
SPLIT LINE 2 SHAPES: twins
SHADED SHAPE: affected with trait
SHAPE W/ BRACKETS O: adopted
HALF SHADED SHAPE: carrier of trait
TRIANGLE: miscarriage
Widow's peak is dominant. Dad can't pass sex-linked trait to son (XY), only to his daughter (XX). However, they have a son with a widow's peak, indicating it isn't an X-linked trait
A child's gender depends on the father's sperm (X or Y) since the egg cell always carries X
X sperm is slow but can survive longer, Y sperm is fast but dies faster
Can only determine homozygous or heterozygous alleles when individuals have children and express a dominant trait
Females who are homozygous and males who are hemizygous express the phenotype in X-linked recessive inheritance
An affected mother passes the trait to all offspring but only sons exhibit the phenotypes in X-linked recessive inheritance
An affected father passes the trait to all daughters but to none of his sons in X-linked recessive inheritance
Individuals with the dominant allele on the X chromosome exhibit the phenotype
An affected male passes the allele to all daughters but to none of his sons
An affected female passes the alleles to all offspring unless she is a heterozygote
Linked genes tend to be inherited together because they are located near each other on the same chromosome
Genes located on the same chromosome tend to be inherited together and are called linked genes
Non-parental phenotypes are produced in the test cross through genetic recombination
Identical twins result from one sperm and egg cell dividing during cell division
Conjoined twins were unable to fully divide during cell division
Fraternal twins result from 2 egg cells fertilized by different sperm cells
Large-scale chromosomal alterations in humans and other mammals often lead to spontaneous abortions
In nondisjunction, pairs of chromosomes do not separate properly during meiosis
Alterations of chromosome number or structure cause some genetic disorders
Nondisjunction
Pairs of homologous chromosomes do not separate normally during meiosis
If nondisjunction happens during meiosis 1, it is more severe with: 2 gametes with extra, 2 gametes with missing chromosomes
As a result of nondisjunction, one gamete receives two of the same type of chromosome, and another gamete receives no copy
Aneuploidy results from the fertilization of gametes in which nondisjunction occurred
Offspring with aneuploidy have an abnormal number of a particular chromosome
A monosomic zygote has only one copy of a particular chromosome, often leading to miscarriages
A trisomic zygote has three copies of a particular chromosome, with a higher survival rate
Polyploidy is a condition in which an organism has more than two complete sets of chromosomes
Polyploidy is common in plants but not animals
Polyploids are more normal in appearance than aneuploids
Down syndrome (Trisomy 21) results from 3 copies of chromosome 21
Down syndrome affects about one out of every 830 children born in the United States
The frequency of Down syndrome increases with the age of the mother
Klinefelter syndrome results from an extra X chromosome in males, producing XXY individuals
Trisomy X or XXX females occur with a frequency of about one in 1,000 and are at risk for learning disabilities
Monosomy X, called Turner syndrome, produces X0 females who are sterile