DNA Genes And Chromosones Flashcards
How does eukaryotic DNA fit in the nucleus
The negatively charged (PO3-) DNA is tightly wrapped around the positively charged histone proteins to form the complex called chromatin
What changes structurally after DNA replicates
-The replicated chromatin coils up tight around histones to create chromosomes
-Visible under microscope
-X shaped
-Each identical arm is called a sister chromatid
-Pairs of chromatids are joined at the centromere
What is a Karyotype
It’s a method of studying individual chromosomes whilst dividing under a microscope
Why/How do we Karyotype babies
-To screen and indicate some genetic disorders based on the number/length of chromosomes
Eg. Trisome 21, when you have 3 of the 21 chromosome which leads to down syndrome
-Removing amniotic fluid
How do we Karyotype
By dying dividing cells with a special fluorescent dye and then examining and photographing them under a microscope whilst dividing
What features does the Karyotype display
1 - The species from a sample by the number of chromosomes
2 - The species by chromosomes size, shape, and banding pattern
3 - The homologous pairs
4 - The gender of the species Female=homogenous
Males=non-homogenous
What are homologous pairs in chromosomes
A pair of chromosomes with identical size shape and banding pattern
What are autosomes
Non-sex chromosomes (1-22)
What are heterosomes
Sex chromosomes (23)
What are banding patterns
In karyotypes
Loosely coiled = more dye binds so appears darker
Tightly coiled = less dye binds so appears lighter
What’s a genome
The sum of all the genes in an organism
What % of eukaryotic DNA codes for polypeptides
2%
What are the two types of non-coding DNA
-Introns (interruption sequences)
-satellite DNA
What are introns
Interruption sequences which is the non coding region of DNA WITHIN a gene
These are usually longer than exons
What are exons
Expressed sequences which are the coding regions of DNA WITHIN genes
What’s satellite DNA
Non-coding regions of DNA between genes
Often contains simple base sequences repeated many times
What are the functions of non-coding DNA
-Structural (helps coil DNA molecules into chromosomes)
-Control (regulates gene expression)
-DNA replication
-Storage of unused copies of genes (pseudogenes)
