Genes and Inheritance Flashcards
What are the stages of mitosis
Interphase, Prophase, Metaphase, Anaphase and Telophase
What happens in interphase
Chromosomes are diffuse (uncondensed and not visible)
RNA and protein synthesis
DNA Synthesis during S Phase
Cell Growth
What happens in prophase
replicated chromosomes become visible
comprised of sister chromatids joined by centromeres
the nuclear membrane breaks down
centrioles move to opposite poles, with spindle fibres produced between them
what happens in metaphase
chromosomes attach to the spindle fibres by the kinetochores
line up in the equator of the spindle
chromosomes are now at the most condensed state and visible
What happens during anaphase
centromeres divide
sister chromatids pulled apart to the poles by connecting spindle fibres
what happens during telophase
nuclear membranes reform
the chromosomes decondense
the daughter cells return to interphase
why have chromosomes condensed
serve to manoeuvre DNA through cell division
all the cell to avoid getting knotted DNA
What untangles DNA and how
topoisomerase
briefly cut and rejoin DNA
What are somatic cells (chromosomal speaking)
Diploid
What are germ cells (chromosomal speaking)
Diploid or haploid
What is meiosis
the reduction of chromosomal numbers from diploid to haploid
What are the stages of meiosis
Prophase I
Metaphase I
Anaphase I
Telophase I
Prophase II
Metaphase II
Anaphase II
Telophase II
What is a leptotene
when chromosomes first become visible as thin threads within the nucleus
What is a zygotene
the homologous pairs of chromosomes which become closely associated along their lengths by a process called synapsis, to form bivalents
what is a pachytene
synapsis is complete and the bivalents are held together throughout their length by a structure known as the synaptonemal complex
What is recombination
Homologous chromosomes cross over and swap homologous sections of their DNA
what is diplotene
the homologous chromosomes appear to repel each other and remain her together only at chiasmata and at the centromere
what is the chromosomal number during prophase II, metaphase II and anaphase II
haploid
What happens during the second mimic division in the egg
the second mitotic division is not complete until fertilisation, and is very unequal, giving the mature egg and a small polar body
What are Mendel’s two laws
Segregation of characterises
Independant assortment
What is segregation of characteristics
when a pair of characteristics that is only represented in one gamete
What is genetic dominance
when a gene for a characteristic has one dominant allele which stresses the manifestation of the second recessive allele
What is an example of an autosomal recessive disease
Cystic Fibrosis
What are 3 examples of autosomal dominant diseases
Tuberous sclerosis
Neurofibromatosis
Retinoblastoma
What is Independent Assortment
Two characteristics that are inherited independently
What does it mean to describe genes as linked
They are located near each other on a chromosome
What is Sex Linkage
Genes that are carried and inherited via the X and Y chromosomes
Why are males more affected by sex-linked diseases
Males are homozygous, and so recessive alleles manifest themselves in the male phenotype
What are 3 key features of an X-linked recessive pedigree
Clusters of affected males
Affected males connected through unaffected females
No male to male transmission
What are the two Hardy-Weinberg Equilibrium equations
p + q = 1
p^2 + 2pq + q^2 = 1
What are the 5 conditions of Hardy-Weinberg
Infinite population Random mating No selection pressures No new alleles by mutation No net migration into/out of population
What is the human karyotype
44 autosomes (22 pairs) 2 sex chromosomes
When are chromosomes most condensed and visible
during metaphase
What are DNA molecules wrapped around
Histone proteins
What is a histone wrapped with DNA called
Nucleosome
What is a bundle of nucleosomes called
Chromatin Fibre
What do Chromatin Fibres bind to
Scaffold
What does loops of chromatin fibre form
Chromatid
What are two chromatids joined together called
Sister Chromatids
What hold the sister chromatids together
The centromere
What are the names of the different grooves in DNA
Major and Minor Groove
What are telomeres
Short tenderly repeating sequences that prevent DNA fusing and karyotype re-arrangement
Maintain the length of the germ-line cells
What natural process causes shortening of telomeres
Ageing
What is X inactivation
When a maternal chromosome condenses, silencing the gene
What are the 4 stages of the cell cycle
G1
S
G2
M
What does a gene consist of
All DNA sequences necessary to produce a single polypeptide or RNA product
Simply, what is Transcription
DNA -> mRNA
Simply, What is translation
mRNA -> Protein
What 3 areas of a gene are unique to eukaryotic cells
Promoter region
exons
introns
What is the genetic locus
A specific position or location on a chromosome
What is an Allele
An alternate version of a DNA nucleotide sequence that may be t a given locus
What is Diploid
Having maternal and paternal homologous chromosomes
What is haploid
having only one of the two homologous chromosomes
What is homozygous
Having the same alleys at a genetic sequence
What is heterozygous
having different alleles at a genetic locus
What is dominant
traits that are expressed in heterozygotes
What are recessive traits
Traits that are expressed only in homozygotes
