Genetics Flashcards
Describe the human genome?
the complete set of nuclei acid sequences for humans, encoded as DNA within the 23 chromosome pairs in cell nuclei and in a small DNA molecule food within individual mitochondria
Define chromosome
a thread-like structure of nuclei acids and protein found in the nucleus of most living cells, carrying genetic information in the forms of genes
Define locus
the position of a gene along the chromosome
Define gene
a length of DNA encoding the information to make a protein
Define DNA
a self-replicating material which is present in nearly all living organisms as the main constituent of chromosomes - it is the carrier of genetic information
Explain the structure of chromosome
- each is a single molecule of DNA, tightly packaged by proteins with genres located at positions along the chromosome in a linear sequence
Describe the position of genes along the chromosomes
located at positions along the chromosome in a linear sequence
What are homologous chromosomes?
in our body cells each chromosome is paired i.e. forms a homologous pair - one paternal and one maternal - homologous chromosomes contain the same genes
What is a human karyotype?
the number and visual appearance of the chromosomes in the cell nuclei of an organism or species
What is the word for chromosome 1-22?
autosomes
What are X and Y chromosomes?
sex chromosomes
What are the female chromosomes?
XX
What are the male chromosomes?
XY
Define alleles
an allele is a version of a gene - X and Y have two alleles
Define ploidy
the number of sets of chromosomes in each cell
Define haploid
one set of chromosomes
Define diploid
two sets of chromosomes
Define mitosis
normal cell division, creating two genetically-identical daughter cells
Define meiosis
reduction division in which each daughter cell receives one cope of each chromosomes
Briefly explain the human life cycle
- egg and sperm cells (haploid n=23)
- ^ carry one copy of each chromosomes in their nucleus
- at fertilisation, the egg and sperm cell nuclei fuse
- the zygote (fertilised egg) therefore is diploid (2n=46)
- ^ mean it has a copy of each haploid chromosome
What percentage of 1st trimester miscarriages are caused by chromosomal abnormalities?
50%
What is a change in the number of chromosomes usually caused by?
usually an isolated occurrence
What is a change in the structure of chromosomes usually caused by?
translocations, may be inherited
How many newborns in 200 have multiple congenital abnormalities?
1
What chromosomal abnormality is trisomy 13?
patau’s syndrome
What chromosomal abnormality is trisomy 18?
edward’s syndrome
What chromosomal abnormality is trisomy 21?
down’s syndrome
Chromosomal abnormalities are reliant on base-pairing rules. What are the pairs?
A-T
G-C
What is DNA replication?
the copying of genetic material whereby the two strands ‘unzip’ and rejoin using base-pairing rules in 2 identical DNA strands
During the ‘flow of genetic info’ otherwise known as transcription and translation, what occurs?
DNA which is made up of A, T, G, C are unziped to be RNA. mRNA goes in, makes a copy of the DNA where amino acids are created in order to make proteins
What input do proteins have in the human genome?
genes are used to direct the synthesis of proteins in the cells. the proteins take part in our development from the egg to the adult
Explain where variation in human genome occur?
variation in the sequence of the genes contribute to variations between individuals and some inherited genetic variants lead to genetic diseases e.g. cystic fibrosis
