Biology Chapter 12 Complex Inheritance

gonads

an organ that produces gametes; a testis or ovary

autosomes

any chromosome that is not a sex chromosome; 22 pairs

sex chromosomes

a chromosome involved with determining the sex of an organism; one from each parent; one pair

X-linked trait

phenotype determined by an allele on an X chromosome

pedigree

following a trait through several generations. cover at least 3 generations. male - squares. female - circles

Y-chromosome analysis

comparing STR sequences on the Y chromosome to examine paternity and paternal ancestry

codominance

a form of inheritance in which both alleles contribute equally to the phenotype

continuous variation

variation in a population showing an unbroken range of phenotypes rather than discrete categories

polygenic trait

trait whose phenotype is determined by the interaction among alleles of more than one gene

multifactorial inheritance

interaction between genes and the environment that contribute to a phenotype or trait

aneuploidy

off number of chromosomes; 45 or 47

nondisjunction

failure of chromosomes to separate during cell division; leads to an odd number of chromosomes

trisomy 21

carrying an extra copy of chromosome 21; down syndrome

amniocentesis

producer that removes fluid surrounding the fetus to obtain and analyze fetal cells to diagnose genetic disorders

karyotype

picture or depiction of all the chromosomes of one person. karyotype analysis can be used to detect trisomy 21 prenatally

incomplete dominance

situation in which one allele is not completely dominant over another

intersex

pertaining to a group of conditions reflecting a discrepancy between external and internal genitalia

Duchenne muscular dystrophy

an X-linked condition with symmetrical weakness and wasting of pelvic, shoulder, and proximal limb muscles

SRY gene

Sex determining region of the Y chromosome

short tandem repeat (STR)

short sequences of DNA repeated many times in a row

Rh factor

refers to the presence or absence of the Rh antigen on red blood cells

continuous variation

range of small differences in a shared trait

clinical depression

a feeling of sadness and hopelessness that can last months