6.4 Homologous chromosomes, autosomes and sex chromosomes Flashcards
What does homologous chromosomes mean?
Matching pairs of chromosomes that have the same genes at the same positions but not necessarily the same alleles
What does locus mean?
The position of a gene on a chromosome, plural=loci
What does non-homologus mean?
Non-matching chromosomes that do not have the same gene loci
What does ideogram mean?
a stylised representation of a haploid ste of chromosomes arranged by decreasing size
Where do the chromosome pairs come from?
One from dad and one from mum
What are sex chromosomes?
A pair of chromosomes that differ in males and females that determine the sex ; allosomes
What is an autosome?
Any one of a pair of homologous chromosomes that are identical in appearance in both males and females; cannot determine sex
What is a centromere?
The position where the chromatids are held together in a chromosome
What are the sex chromosomes of females and males?
XX = female
XY = male
How many autosomes are there in humans?
44, 22 pairs; one odd pair which are the allosomes
How are autosomes distinguished by?
-their relative size
-position of the centromere
-patterns of light and dark bands from special staining techniques
What does the larger chromosome contain?
More DNA and a large number of genes
What is meiosis?
A type of cell division that prodcues haploid gametes
What is environmental sex determination (ESD)?
The sex of the offspring is established by environmental conditions rather than genetic factors
What is the % of a sperm cell carying and X or Y chromosome?
50%
