3.2 Flashcards
Homologous chromosomes are chromosomes that share:
- the same structural features
- the same genes at the same loci positions
Which chromosome is shorter out of the X & the Y
the Y chromosome
Two ways a karyogram can be used:
- to deduce sex
- to diagnose Down Syndrome (trisomy 21)
Features of plasmids
- Naked DNA - not associated w histone proteins
- Small circular rings of DNA
- Not responsible for normal life processes
- Commonly contain survival characteristics -e.g antibiotic resistence
- Can be passed between prokaryotes
- Can be incorporated into the nucleoid chromosome
How can chromosomes vary?
- length - number of base pairs in DNA molecule
- position of the centromere
- genes occur at a specific locus
What is the N number
number of chromosomes possessed by a species
How many chromosomes do humans have?
23 different chromosomes
Diploid nucleus
Has 2 of each chromosome - therefore have 2 copies of every gene
Haploid nucleus
Has 1 of each chromosome
What type of nuclei do gametes have?
Haploid nuclei
Which type of nuclei are less susceptible to disease?
Diploid nuclei - have 2 copies of gene so organism is more likely to possess a healthy copy
How many diploid chromosomes in each human cell?
46
Are body cells (somatic cells) haploid or diploid?
diploid
How human chromosome pairs are homologous?
22
Why is X bigger than the Y?
X carries many genes in the non-homologous region which are not present on Y
What is genome size?
total number of DNA base pairs in 1 copy of a haploid genome
What is a karyogram?
diagram or photographs present in a nucleus (of a eukaryotic cell) arranged in homologous pairs of decreasing length
What is the karyotype?
the number and type of chromosomes present in a cell
How many chromosomes do prokaryotes have?
1
what do diploid nuclei have?
pairs of homologous chromosomes
What is the centromere?
the area of the chromosome where sister chromatids are linked. During cell division, it is where the spindle fibres attach.
What are sister chromatids?
2 DNA molecules formed by DNA replication prior to cell division until the splitting of the centromere at the start of anaphase
How many different chromosomes do humans have?
23
Different chromosomes contain different what?
different genes
What does Cairn’s technique involve when measuring the length of DNA molecules?
autoradiography & electron microscopy
What are karyograms used for?
- determine sex
- detect chromosome abnormalities
